Best Practices for Speeding Up Your Web Site

Minimize HTTP Requests

tag: content

80% of the end-user response time is spent on the front-end. Most of this time is tied up in downloading all the components in the page: images, stylesheets, scripts, Flash, etc. Reducing the number of components in turn reduces the number of HTTP requests required to render the page. This is the key to faster pages.

One way to reduce the number of components in the page is to simplify the page's design. But is there a way to build pages with richer content while also achieving fast response times? Here are some techniques for reducing the number of HTTP requests, while still supporting rich page designs.

Combined files are a way to reduce the number of HTTP requests by combining all scripts into a single script, and similarly combining all CSS into a single stylesheet. Combining files is more challenging when the scripts and stylesheets vary from page to page, but making this part of your release process improves response times.

CSS Sprites are the preferred method for reducing the number of image requests. Combine your background images into a single image and use the CSS background-image and background-position properties to display the desired image segment.

Image maps combine multiple images into a single image. The overall size is about the same, but reducing the number of HTTP requests speeds up the page. Image maps only work if the images are contiguous in the page, such as a navigation bar. Defining the coordinates of image maps can be tedious and error prone. Using image maps for navigation is not accessible too, so it's not recommended.

Inline images use the data: URL scheme to embed the image data in the actual page. This can increase the size of your HTML document. Combining inline images into your (cached) stylesheets is a way to reduce HTTP requests and avoid increasing the size of your pages. Inline images are not yet supported across all major browsers.

Reducing the number of HTTP requests in your page is the place to start. This is the most important guideline for improving performance for first time visitors. As described in Tenni Theurer's blog post Browser Cache Usage - Exposed!, 40-60% of daily visitors to your site come in with an empty cache. Making your page fast for these first time visitors is key to a better user experience.

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Use a Content Delivery Network

tag: server

The user's proximity to your web server has an impact on response times. Deploying your content across multiple, geographically dispersed servers will make your pages load faster from the user's perspective. But where should you start?

As a first step to implementing geographically dispersed content, don't attempt to redesign your web application to work in a distributed architecture. Depending on the application, changing the architecture could include daunting tasks such as synchronizing session state and replicating database transactions across server locations. Attempts to reduce the distance between users and your content could be delayed by, or never pass, this application architecture step.

Remember that 80-90% of the end-user response time is spent downloading all the components in the page: images, stylesheets, scripts, Flash, etc. This is the Performance Golden Rule. Rather than starting with the difficult task of redesigning your application architecture, it's better to first disperse your static content. This not only achieves a bigger reduction in response times, but it's easier thanks to content delivery networks.

A content delivery network (CDN) is a collection of web servers distributed across multiple locations to deliver content more efficiently to users. The server selected for delivering content to a specific user is typically based on a measure of network proximity. For example, the server with the fewest network hops or the server with the quickest response time is chosen.

Some large Internet companies own their own CDN, but it's cost-effective to use a CDN service provider, such as Akamai Technologies, Mirror Image Internet, or Limelight Networks. For start-up companies and private web sites, the cost of a CDN service can be prohibitive, but as your target audience grows larger and becomes more global, a CDN is necessary to achieve fast response times. At Yahoo!, properties that moved static content off their application web servers to a CDN improved end-user response times by 20% or more. Switching to a CDN is a relatively easy code change that will dramatically improve the speed of your web site.

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Add an Expires or a Cache-Control Header

tag: server

There are two aspects to this rule:

• For static components: implement "Never expire" policy by setting far future Expires header


• For dynamic components: use an appropriate Cache-Control header to help the browser with conditional requests

Web page designs are getting richer and richer, which means more scripts, stylesheets, images, and Flash in the page. A first-time visitor to your page may have to make several HTTP requests, but by using the Expires header you make those components cacheable. This avoids unnecessary HTTP requests on subsequent page views. Expires headers are most often used with images, but they should be used on all components including scripts, stylesheets, and Flash components.

Browsers (and proxies) use a cache to reduce the number and size of HTTP requests, making web pages load faster. A web server uses the Expires header in the HTTP response to tell the client how long a component can be cached. This is a far future Expires header, telling the browser that this response won't be stale until April 15, 2010.

      Expires: Thu, 15 Apr 2010 20:00:00 GMT

If your server is Apache, use the ExpiresDefault directive to set an expiration date relative to the current date. This example of the ExpiresDefault directive sets the Expires date 10 years out from the time of the request.

      ExpiresDefault "access plus 10 years"

Keep in mind, if you use a far future Expires header you have to change the component's filename whenever the component changes. At Yahoo! we often make this step part of the build process: a version number is embedded in the component's filename, for example, yahoo_2.0.6.js.

Using a far future Expires header affects page views only after a user has already visited your site. It has no effect on the number of HTTP requests when a user visits your site for the first time and the browser's cache is empty. Therefore the impact of this performance improvement depends on how often users hit your pages with a primed cache. (A "primed cache" already contains all of the components in the page.) We measured this at Yahoo! and found the number of page views with a primed cache is 75-85%. By using a far future Expires header, you increase the number of components that are cached by the browser and re-used on subsequent page views without sending a single byte over the user's Internet connection.

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Gzip Components

tag: server

The time it takes to transfer an HTTP request and response across the network can be significantly reduced by decisions made by front-end engineers. It's true that the end-user's bandwidth speed, Internet service provider, proximity to peering exchange points, etc. are beyond the control of the development team. But there are other variables that affect response times. Compression reduces response times by reducing the size of the HTTP response.

Starting with HTTP/1.1, web clients indicate support for compression with the Accept-Encoding header in the HTTP request.

      Accept-Encoding: gzip, deflate

If the web server sees this header in the request, it may compress the response using one of the methods listed by the client. The web server notifies the web client of this via the Content-Encoding header in the response.

      Content-Encoding: gzip

Gzip is the most popular and effective compression method at this time. It was developed by the GNU project and standardized by RFC 1952. The only other compression format you're likely to see is deflate, but it's less effective and less popular.

Gzipping generally reduces the response size by about 70%. Approximately 90% of today's Internet traffic travels through browsers that claim to support gzip. If you use Apache, the module configuring gzip depends on your version: Apache 1.3 uses mod_gzip while Apache 2.x uses mod_deflate.

There are known issues with browsers and proxies that may cause a mismatch in what the browser expects and what it receives with regard to compressed content. Fortunately, these edge cases are dwindling as the use of older browsers drops off. The Apache modules help out by adding appropriate Vary response headers automatically.

Servers choose what to gzip based on file type, but are typically too limited in what they decide to compress. Most web sites gzip their HTML documents. It's also worthwhile to gzip your scripts and stylesheets, but many web sites miss this opportunity. In fact, it's worthwhile to compress any text response including XML and JSON. Image and PDF files should not be gzipped because they are already compressed. Trying to gzip them not only wastes CPU but can potentially increase file sizes.

Gzipping as many file types as possible is an easy way to reduce page weight and accelerate the user experience.

Put Stylesheets at the Top

tag: css

While researching performance at Yahoo!, we discovered that moving stylesheets to the document HEAD makes pages appear to be loading faster. This is because putting stylesheets in the HEAD allows the page to render progressively.

Front-end engineers that care about performance want a page to load progressively; that is, we want the browser to display whatever content it has as soon as possible. This is especially important for pages with a lot of content and for users on slower Internet connections. The importance of giving users visual feedback, such as progress indicators, has been well researched and documented. In our case the HTML page is the progress indicator! When the browser loads the page progressively the header, the navigation bar, the logo at the top, etc. all serve as visual feedback for the user who is waiting for the page. This improves the overall user experience.

The problem with putting stylesheets near the bottom of the document is that it prohibits progressive rendering in many browsers, including Internet Explorer. These browsers block rendering to avoid having to redraw elements of the page if their styles change. The user is stuck viewing a blank white page.

The HTML specification clearly states that stylesheets are to be included in the HEAD of the page: "Unlike A, [LINK] may only appear in the HEAD section of a document, although it may appear any number of times." Neither of the alternatives, the blank white screen or flash of unstyled content, are worth the risk. The optimal solution is to follow the HTML specification and load your stylesheets in the document HEAD.

Put Scripts at the Bottom

tag: javascript

The problem caused by scripts is that they block parallel downloads. The HTTP/1.1 specification suggests that browsers download no more than two components in parallel per hostname. If you serve your images from multiple hostnames, you can get more than two downloads to occur in parallel. While a script is downloading, however, the browser won't start any other downloads, even on different hostnames.

In some situations it's not easy to move scripts to the bottom. If, for example, the script uses document.write to insert part of the page's content, it can't be moved lower in the page. There might also be scoping issues. In many cases, there are ways to workaround these situations.

An alternative suggestion that often comes up is to use deferred scripts. The DEFER attribute indicates that the script does not contain document.write, and is a clue to browsers that they can continue rendering. Unfortunately, Firefox doesn't support the DEFER attribute. In Internet Explorer, the script may be deferred, but not as much as desired. If a script can be deferred, it can also be moved to the bottom of the page. That will make your web pages load faster.

Avoid CSS Expressions

tag: css

CSS expressions are a powerful (and dangerous) way to set CSS properties dynamically. They were supported in Internet Explorer starting with version 5, but were deprecated starting with IE8. As an example, the background color could be set to alternate every hour using CSS expressions:

      background-color: expression( (new Date()).getHours()%2 ? "#B8D4FF" : "#F08A00" );

As shown here, the expression method accepts a JavaScript expression. The CSS property is set to the result of evaluating the JavaScript expression. The expression method is ignored by other browsers, so it is useful for setting properties in Internet Explorer needed to create a consistent experience across browsers.

The problem with expressions is that they are evaluated more frequently than most people expect. Not only are they evaluated when the page is rendered and resized, but also when the page is scrolled and even when the user moves the mouse over the page. Adding a counter to the CSS expression allows us to keep track of when and how often a CSS expression is evaluated. Moving the mouse around the page can easily generate more than 10,000 evaluations.

One way to reduce the number of times your CSS expression is evaluated is to use one-time expressions, where the first time the expression is evaluated it sets the style property to an explicit value, which replaces the CSS expression. If the style property must be set dynamically throughout the life of the page, using event handlers instead of CSS expressions is an alternative approach. If you must use CSS expressions, remember that they may be evaluated thousands of times and could affect the performance of your page.

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Make JavaScript and CSS External

tag: javascript, css

Many of these performance rules deal with how external components are managed. However, before these considerations arise you should ask a more basic question: Should JavaScript and CSS be contained in external files, or inlined in the page itself?

Using external files in the real world generally produces faster pages because the JavaScript and CSS files are cached by the browser. JavaScript and CSS that are inlined in HTML documents get downloaded every time the HTML document is requested. This reduces the number of HTTP requests that are needed, but increases the size of the HTML document. On the other hand, if the JavaScript and CSS are in external files cached by the browser, the size of the HTML document is reduced without increasing the number of HTTP requests.

The key factor, then, is the frequency with which external JavaScript and CSS components are cached relative to the number of HTML documents requested. This factor, although difficult to quantify, can be gauged using various metrics. If users on your site have multiple page views per session and many of your pages re-use the same scripts and stylesheets, there is a greater potential benefit from cached external files.

Many web sites fall in the middle of these metrics. For these sites, the best solution generally is to deploy the JavaScript and CSS as external files. The only exception where inlining is preferable is with home pages, such as Yahoo!'s front page and My Yahoo!. Home pages that have few (perhaps only one) page view per session may find that inlining JavaScript and CSS results in faster end-user response times.

For front pages that are typically the first of many page views, there are techniques that leverage the reduction of HTTP requests that inlining provides, as well as the caching benefits achieved through using external files. One such technique is to inline JavaScript and CSS in the front page, but dynamically download the external files after the page has finished loading. Subsequent pages would reference the external files that should already be in the browser's cache.

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Reduce DNS Lookups

tag: content

The Domain Name System (DNS) maps hostnames to IP addresses, just as phonebooks map people's names to their phone numbers. When you type www.yahoo.com into your browser, a DNS resolver contacted by the browser returns that server's IP address. DNS has a cost. It typically takes 20-120 milliseconds for DNS to lookup the IP address for a given hostname. The browser can't download anything from this hostname until the DNS lookup is completed.

DNS lookups are cached for better performance. This caching can occur on a special caching server, maintained by the user's ISP or local area network, but there is also caching that occurs on the individual user's computer. The DNS information remains in the operating system's DNS cache (the "DNS Client service" on Microsoft Windows). Most browsers have their own caches, separate from the operating system's cache. As long as the browser keeps a DNS record in its own cache, it doesn't bother the operating system with a request for the record.

Internet Explorer caches DNS lookups for 30 minutes by default, as specified by the DnsCacheTimeout registry setting. Firefox caches DNS lookups for 1 minute, controlled by the network.dnsCacheExpiration configuration setting. (Fasterfox changes this to 1 hour.)

When the client's DNS cache is empty (for both the browser and the operating system), the number of DNS lookups is equal to the number of unique hostnames in the web page. This includes the hostnames used in the page's URL, images, script files, stylesheets, Flash objects, etc. Reducing the number of unique hostnames reduces the number of DNS lookups.

Reducing the number of unique hostnames has the potential to reduce the amount of parallel downloading that takes place in the page. Avoiding DNS lookups cuts response times, but reducing parallel downloads may increase response times. My guideline is to split these components across at least two but no more than four hostnames. This results in a good compromise between reducing DNS lookups and allowing a high degree of parallel downloads.

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Minify JavaScript and CSS

tag: javascript, css

Minification is the practice of removing unnecessary characters from code to reduce its size thereby improving load times. When code is minified all comments are removed, as well as unneeded white space characters (space, newline, and tab). In the case of JavaScript, this improves response time performance because the size of the downloaded file is reduced. Two popular tools for minifying JavaScript code are JSMin and YUI Compressor. The YUI compressor can also minify CSS.

Obfuscation is an alternative optimization that can be applied to source code. It's more complex than minification and thus more likely to generate bugs as a result of the obfuscation step itself. In a survey of ten top U.S. web sites, minification achieved a 21% size reduction versus 25% for obfuscation. Although obfuscation has a higher size reduction, minifying JavaScript is less risky.

In addition to minifying external scripts and styles, inlined <script> and <style> blocks can and should also be minified. Even if you gzip your scripts and styles, minifying them will still reduce the size by 5% or more. As the use and size of JavaScript and CSS increases, so will the savings gained by minifying your code.

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Avoid Redirects

tag: content

Redirects are accomplished using the 301 and 302 status codes. Here's an example of the HTTP headers in a 301 response:

      HTTP/1.1 301 Moved Permanently        Location: http://example.com/newuri        Content-Type: text/html

The browser automatically takes the user to the URL specified in the Location field. All the information necessary for a redirect is in the headers. The body of the response is typically empty. Despite their names, neither a 301 nor a 302 response is cached in practice unless additional headers, such as Expires or Cache-Control, indicate it should be. The meta refresh tag and JavaScript are other ways to direct users to a different URL, but if you must do a redirect, the preferred technique is to use the standard 3xx HTTP status codes, primarily to ensure the back button works correctly.

The main thing to remember is that redirects slow down the user experience. Inserting a redirect between the user and the HTML document delays everything in the page since nothing in the page can be rendered and no components can start being downloaded until the HTML document has arrived.

One of the most wasteful redirects happens frequently and web developers are generally not aware of it. It occurs when a trailing slash (/) is missing from a URL that should otherwise have one. For example, going to http://astrology.yahoo.com/astrology results in a 301 response containing a redirect to http://astrology.yahoo.com/astrology/ (notice the added trailing slash). This is fixed in Apache by using Alias or mod_rewrite, or the DirectorySlash directive if you're using Apache handlers.

Connecting an old web site to a new one is another common use for redirects. Others include connecting different parts of a website and directing the user based on certain conditions (type of browser, type of user account, etc.). Using a redirect to connect two web sites is simple and requires little additional coding. Although using redirects in these situations reduces the complexity for developers, it degrades the user experience. Alternatives for this use of redirects include using Alias and mod_rewrite if the two code paths are hosted on the same server. If a domain name change is the cause of using redirects, an alternative is to create a CNAME (a DNS record that creates an alias pointing from one domain name to another) in combination with Alias or mod_rewrite.

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Remove Duplicate Scripts

tag: javascript

It hurts performance to include the same JavaScript file twice in one page. This isn't as unusual as you might think. A review of the ten top U.S. web sites shows that two of them contain a duplicated script. Two main factors increase the odds of a script being duplicated in a single web page: team size and number of scripts. When it does happen, duplicate scripts hurt performance by creating unnecessary HTTP requests and wasted JavaScript execution.

Unnecessary HTTP requests happen in Internet Explorer, but not in Firefox. In Internet Explorer, if an external script is included twice and is not cacheable, it generates two HTTP requests during page loading. Even if the script is cacheable, extra HTTP requests occur when the user reloads the page.

In addition to generating wasteful HTTP requests, time is wasted evaluating the script multiple times. This redundant JavaScript execution happens in both Firefox and Internet Explorer, regardless of whether the script is cacheable.

One way to avoid accidentally including the same script twice is to implement a script management module in your templating system. The typical way to include a script is to use the SCRIPT tag in your HTML page.

      <script type="text/javascript" src="menu_1.0.17.js"></script>

An alternative in PHP would be to create a function called insertScript.

      <?php insertScript("menu.js") ?>

In addition to preventing the same script from being inserted multiple times, this function could handle other issues with scripts, such as dependency checking and adding version numbers to script filenames to support far future Expires headers.

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Configure ETags

tag: server

Entity tags (ETags) are a mechanism that web servers and browsers use to determine whether the component in the browser's cache matches the one on the origin server. (An "entity" is another word a "component": images, scripts, stylesheets, etc.) ETags were added to provide a mechanism for validating entities that is more flexible than the last-modified date. An ETag is a string that uniquely identifies a specific version of a component. The only format constraints are that the string be quoted. The origin server specifies the component's ETag using the ETag response header.

      HTTP/1.1 200 OK        Last-Modified: Tue, 12 Dec 2006 03:03:59 GMT        ETag: "10c24bc-4ab-457e1c1f"        Content-Length: 12195

Later, if the browser has to validate a component, it uses the If-None-Match header to pass the ETag back to the origin server. If the ETags match, a 304 status code is returned reducing the response by 12195 bytes for this example.

      GET /i/yahoo.gif HTTP/1.1        Host: us.yimg.com        If-Modified-Since: Tue, 12 Dec 2006 03:03:59 GMT        If-None-Match: "10c24bc-4ab-457e1c1f"        HTTP/1.1 304 Not Modified

The problem with ETags is that they typically are constructed using attributes that make them unique to a specific server hosting a site. ETags won't match when a browser gets the original component from one server and later tries to validate that component on a different server, a situation that is all too common on Web sites that use a cluster of servers to handle requests. By default, both Apache and IIS embed data in the ETag that dramatically reduces the odds of the validity test succeeding on web sites with multiple servers.

The ETag format for Apache 1.3 and 2.x is inode-size-timestamp. Although a given file may reside in the same directory across multiple servers, and have the same file size, permissions, timestamp, etc., its inode is different from one server to the next.

IIS 5.0 and 6.0 have a similar issue with ETags. The format for ETags on IIS is Filetimestamp:ChangeNumber. A ChangeNumber is a counter used to track configuration changes to IIS. It's unlikely that the ChangeNumber is the same across all IIS servers behind a web site.

The end result is ETags generated by Apache and IIS for the exact same component won't match from one server to another. If the ETags don't match, the user doesn't receive the small, fast 304 response that ETags were designed for; instead, they'll get a normal 200 response along with all the data for the component. If you host your web site on just one server, this isn't a problem. But if you have multiple servers hosting your web site, and you're using Apache or IIS with the default ETag configuration, your users are getting slower pages, your servers have a higher load, you're consuming greater bandwidth, and proxies aren't caching your content efficiently. Even if your components have a far future Expires header, a conditional GET request is still made whenever the user hits Reload or Refresh.

If you're not taking advantage of the flexible validation model that ETags provide, it's better to just remove the ETag altogether. The Last-Modified header validates based on the component's timestamp. And removing the ETag reduces the size of the HTTP headers in both the response and subsequent requests. This Microsoft Support article describes how to remove ETags. In Apache, this is done by simply adding the following line to your Apache configuration file:

      FileETag none

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Make Ajax Cacheable

tag: content

One of the cited benefits of Ajax is that it provides instantaneous feedback to the user because it requests information asynchronously from the backend web server. However, using Ajax is no guarantee that the user won't be twiddling his thumbs waiting for those asynchronous JavaScript and XML responses to return. In many applications, whether or not the user is kept waiting depends on how Ajax is used. For example, in a web-based email client the user will be kept waiting for the results of an Ajax request to find all the email messages that match their search criteria. It's important to remember that "asynchronous" does not imply "instantaneous".

To improve performance, it's important to optimize these Ajax responses. The most important way to improve the performance of Ajax is to make the responses cacheable, as discussed in Add an Expires or a Cache-Control Header. Some of the other rules also apply to Ajax:

• Gzip Components
  
  


• Reduce DNS Lookups
  
  


• Minify JavaScript
  
  


• Avoid Redirects
  
  


• Configure ETags
  
  

Let's look at an example. A Web 2.0 email client might use Ajax to download the user's address book for autocompletion. If the user hasn't modified her address book since the last time she used the email web app, the previous address book response could be read from cache if that Ajax response was made cacheable with a future Expires or Cache-Control header. The browser must be informed when to use a previously cached address book response versus requesting a new one. This could be done by adding a timestamp to the address book Ajax URL indicating the last time the user modified her address book, for example, &t=1190241612. If the address book hasn't been modified since the last download, the timestamp will be the same and the address book will be read from the browser's cache eliminating an extra HTTP roundtrip. If the user has modified her address book, the timestamp ensures the new URL doesn't match the cached response, and the browser will request the updated address book entries.

Even though your Ajax responses are created dynamically, and might only be applicable to a single user, they can still be cached. Doing so will make your Web 2.0 apps faster.

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Flush the Buffer Early

tag: server

When users request a page, it can take anywhere from 200 to 500ms for the backend server to stitch together the HTML page. During this time, the browser is idle as it waits for the data to arrive. In PHP you have the function flush(). It allows you to send your partially ready HTML response to the browser so that the browser can start fetching components while your backend is busy with the rest of the HTML page. The benefit is mainly seen on busy backends or light frontends.

A good place to consider flushing is right after the HEAD because the HTML for the head is usually easier to produce and it allows you to include any CSS and JavaScript files for the browser to start fetching in parallel while the backend is still processing.

Example:

      ... <!-- css, js -->      </head>      <?php flush(); ?>      <body>        ... <!-- content -->  

Yahoo! search pioneered research and real user testing to prove the benefits of using this technique.

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Use GET for AJAX Requests

tag: server

The Yahoo! Mail team found that when using XMLHttpRequest, POST is implemented in the browsers as a two-step process: sending the headers first, then sending data. So it's best to use GET, which only takes one TCP packet to send (unless you have a lot of cookies). The maximum URL length in IE is 2K, so if you send more than 2K data you might not be able to use GET.

An interesting side affect is that POST without actually posting any data behaves like GET. Based on the HTTP specs, GET is meant for retrieving information, so it makes sense (semantically) to use GET when you're only requesting data, as opposed to sending data to be stored server-side.

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Post-load Components

tag: content

You can take a closer look at your page and ask yourself: "What's absolutely required in order to render the page initially?". The rest of the content and components can wait.

JavaScript is an ideal candidate for splitting before and after the onload event. For example if you have JavaScript code and libraries that do drag and drop and animations, those can wait, because dragging elements on the page comes after the initial rendering. Other places to look for candidates for post-loading include hidden content (content that appears after a user action) and images below the fold.

Tools to help you out in your effort: YUI Image Loader allows you to delay images below the fold and the YUI Get utility is an easy way to include JS and CSS on the fly. For an example in the wild take a look at Yahoo! Home Page with Firebug's Net Panel turned on.

It's good when the performance goals are inline with other web development best practices. In this case, the idea of progressive enhancement tells us that JavaScript, when supported, can improve the user experience but you have to make sure the page works even without JavaScript. So after you've made sure the page works fine, you can enhance it with some post-loaded scripts that give you more bells and whistles such as drag and drop and animations.

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Preload Components

tag: content

Preload may look like the opposite of post-load, but it actually has a different goal. By preloading components you can take advantage of the time the browser is idle and request components (like images, styles and scripts) you'll need in the future. This way when the user visits the next page, you could have most of the components already in the cache and your page will load much faster for the user.

There are actually several types of preloading:

• Unconditional preload - as soon as onload fires, you go ahead and fetch some extra components. Check google.com for an example of how a sprite image is requested onload. This sprite image is not needed on the google.com homepage, but it is needed on the consecutive search result page.


• Conditional preload - based on a user action you make an educated guess where the user is headed next and preload accordingly. On search.yahoo.com you can see how some extra components are requested after you start typing in the input box.


• Anticipated preload - preload in advance before launching a redesign. It often happens after a redesign that you hear: "The new site is cool, but it's slower than before". Part of the problem could be that the users were visiting your old site with a full cache, but the new one is always an empty cache experience. You can mitigate this side effect by preloading some components before you even launched the redesign. Your old site can use the time the browser is idle and request images and scripts that will be used by the new site

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Reduce the Number of DOM Elements

tag: content

A complex page means more bytes to download and it also means slower DOM access in JavaScript. It makes a difference if you loop through 500 or 5000 DOM elements on the page when you want to add an event handler for example.

A high number of DOM elements can be a symptom that there's something that should be improved with the markup of the page without necessarily removing content. Are you using nested tables for layout purposes? Are you throwing in more <div>s only to fix layout issues? Maybe there's a better and more semantically correct way to do your markup.

A great help with layouts are the YUI CSS utilities: grids.css can help you with the overall layout, fonts.css and reset.css can help you strip away the browser's defaults formatting. This is a chance to start fresh and think about your markup, for example use <div>s only when it makes sense semantically, and not because it renders a new line.

The number of DOM elements is easy to test, just type in Firebug's console:

document.getElementsByTagName('*').length

And how many DOM elements are too many? Check other similar pages that have good markup. For example the Yahoo! Home Page is a pretty busy page and still under 700 elements (HTML tags).

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Split Components Across Domains

tag: content

Splitting components allows you to maximize parallel downloads. Make sure you're using not more than 2-4 domains because of the DNS lookup penalty. For example, you can host your HTML and dynamic content on www.example.org and split static components between static1.example.org and static2.example.org

For more information check "Maximizing Parallel Downloads in the Carpool Lane" by Tenni Theurer and Patty Chi.

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Minimize the Number of iframes

tag: content

Iframes allow an HTML document to be inserted in the parent document. It's important to understand how iframes work so they can be used effectively.

<iframe> pros:

• Helps with slow third-party content like badges and ads


• Security sandbox


• Download scripts in parallel

<iframe> cons:

• Costly even if blank


• Blocks page onload


• Non-semantic

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No 404s

tag: content

HTTP requests are expensive so making an HTTP request and getting a useless response (i.e. 404 Not Found) is totally unnecessary and will slow down the user experience without any benefit.

Some sites have helpful 404s "Did you mean X?", which is great for the user experience but also wastes server resources (like database, etc). Particularly bad is when the link to an external JavaScript is wrong and the result is a 404. First, this download will block parallel downloads. Next the browser may try to parse the 404 response body as if it were JavaScript code, trying to find something usable in it.

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Reduce Cookie Size

tag: cookie

HTTP cookies are used for a variety of reasons such as authentication and personalization. Information about cookies is exchanged in the HTTP headers between web servers and browsers. It's important to keep the size of cookies as low as possible to minimize the impact on the user's response time.

For more information check "When the Cookie Crumbles" by Tenni Theurer and Patty Chi. The take-home of this research:

• Eliminate unnecessary cookies


• Keep cookie sizes as low as possible to minimize the impact on the user response time


• Be mindful of setting cookies at the appropriate domain level so other sub-domains are not affected


• Set an Expires date appropriately. An earlier Expires date or none removes the cookie sooner, improving the user response time

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Use Cookie-free Domains for Components

tag: cookie

When the browser makes a request for a static image and sends cookies together with the request, the server doesn't have any use for those cookies. So they only create network traffic for no good reason. You should make sure static components are requested with cookie-free requests. Create a subdomain and host all your static components there.

If your domain is www.example.org, you can host your static components on static.example.org. However, if you've already set cookies on the top-level domain example.org as opposed to www.example.org, then all the requests to static.example.org will include those cookies. In this case, you can buy a whole new domain, host your static components there, and keep this domain cookie-free. Yahoo! uses yimg.com, YouTube uses ytimg.com, Amazon uses images-amazon.com and so on.

Another benefit of hosting static components on a cookie-free domain is that some proxies might refuse to cache the components that are requested with cookies. On a related note, if you wonder if you should use example.org or www.example.org for your home page, consider the cookie impact. Omitting www leaves you no choice but to write cookies to *.example.org, so for performance reasons it's best to use the www subdomain and write the cookies to that subdomain.

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Minimize DOM Access

tag: javascript

Accessing DOM elements with JavaScript is slow so in order to have a more responsive page, you should:

• Cache references to accessed elements


• Update nodes "offline" and then add them to the tree


• Avoid fixing layout with JavaScript

For more information check the YUI theatre's "High Performance Ajax Applications" by Julien Lecomte.

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Develop Smart Event Handlers

tag: javascript

Sometimes pages feel less responsive because of too many event handlers attached to different elements of the DOM tree which are then executed too often. That's why using event delegation is a good approach. If you have 10 buttons inside a div, attach only one event handler to the div wrapper, instead of one handler for each button. Events bubble up so you'll be able to catch the event and figure out which button it originated from.

You also don't need to wait for the onload event in order to start doing something with the DOM tree. Often all you need is the element you want to access to be available in the tree. You don't have to wait for all images to be downloaded. DOMContentLoaded is the event you might consider using instead of onload, but until it's available in all browsers, you can use the YUI Event utility, which has an onAvailable method.

For more information check the YUI theatre's "High Performance Ajax Applications" by Julien Lecomte.

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Choose <link> over @import

tag: css

One of the previous best practices states that CSS should be at the top in order to allow for progressive rendering.

In IE @import behaves the same as using <link> at the bottom of the page, so it's best not to use it.

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Avoid Filters

tag: css

The IE-proprietary AlphaImageLoader filter aims to fix a problem with semi-transparent true color PNGs in IE versions < 7. The problem with this filter is that it blocks rendering and freezes the browser while the image is being downloaded. It also increases memory consumption and is applied per element, not per image, so the problem is multiplied.

The best approach is to avoid AlphaImageLoader completely and use gracefully degrading PNG8 instead, which are fine in IE. If you absolutely need AlphaImageLoader, use the underscore hack _filter as to not penalize your IE7+ users.

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Optimize Images

tag: images

After a designer is done with creating the images for your web page, there are still some things you can try before you FTP those images to your web server.

• You can check the GIFs and see if they are using a palette size corresponding to the number of colors in the image. Using imagemagick it's easy to check using
  
  identify -verbose image.gif
  
  When you see an image useing 4 colors and a 256 color "slots" in the palette, there is room for improvement.


• Try converting GIFs to PNGs and see if there is a saving. More often than not, there is. Developers often hesitate to use PNGs due to the limited support in browsers, but this is now a thing of the past. The only real problem is alpha-transparency in true color PNGs, but then again, GIFs are not true color and don't support variable transparency either. So anything a GIF can do, a palette PNG (PNG8) can do too (except for animations). This simple imagemagick command results in totally safe-to-use PNGs:
  
  convert image.gif image.png
  
  "All we are saying is: Give PiNG a Chance!"


• Run pngcrush (or any other PNG optimizer tool) on all your PNGs. Example:
  
  pngcrush image.png -rem alla -reduce -brute result.png


• Run jpegtran on all your JPEGs. This tool does lossless JPEG operations such as rotation and can also be used to optimize and remove comments and other useless information (such as EXIF information) from your images.
  
  jpegtran -copy none -optimize -perfect src.jpg dest.jpg

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Optimize CSS Sprites

tag: images

• Arranging the images in the sprite horizontally as opposed to vertically usually results in a smaller file size.


• Combining similar colors in a sprite helps you keep the color count low, ideally under 256 colors so to fit in a PNG8.


• "Be mobile-friendly" and don't leave big gaps between the images in a sprite. This doesn't affect the file size as much but requires less memory for the user agent to decompress the image into a pixel map. 100x100 image is 10 thousand pixels, where 1000x1000 is 1 million pixels

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Don't Scale Images in HTML

tag: images

Don't use a bigger image than you need just because you can set the width and height in HTML. If you need

<img width="100" height="100" src="mycat.jpg" alt="My Cat" />

then your image (mycat.jpg) should be 100x100px rather than a scaled down 500x500px image.

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Make favicon.ico Small and Cacheable

tag: images

The favicon.ico is an image that stays in the root of your server. It's a necessary evil because even if you don't care about it the browser will still request it, so it's better not to respond with a 404 Not Found. Also since it's on the same server, cookies are sent every time it's requested. This image also interferes with the download sequence, for example in IE when you request extra components in the onload, the favicon will be downloaded before these extra components.

So to mitigate the drawbacks of having a favicon.ico make sure:

• It's small, preferably under 1K.


• Set Expires header with what you feel comfortable (since you cannot rename it if you decide to change it). You can probably safely set the Expires header a few months in the future. You can check the last modified date of your current favicon.ico to make an informed decision.

Imagemagick can help you create small favicons

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Keep Components under 25K

tag: mobile

This restriction is related to the fact that iPhone won't cache components bigger than 25K. Note that this is the uncompressed size. This is where minification is important because gzip alone may not be sufficient.

For more information check "Performance Research, Part 5: iPhone Cacheability - Making it Stick" by Wayne Shea and Tenni Theurer.

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Pack Components into a Multipart Document

tag: mobile

Packing components into a multipart document is like an email with attachments, it helps you fetch several components with one HTTP request (remember: HTTP requests are expensive). When you use this technique, first check if the user agent supports it (iPhone does not).

Avoid Empty Image src

tag: server

Image with empty string src attribute occurs more than one will expect. It appears in two form:

1. straight HTML
   
   

   <img src="">

   
   


2. JavaScript
   
   

   var img = new Image();
   
   img.src = "";

   
   

Both forms cause the same effect: browser makes another request to your server.

• Internet Explorer makes a request to the directory in which the page is located.


• Safari and Chrome make a request to the actual page itself.


• Firefox 3 and earlier versions behave the same as Safari and Chrome, but version 3.5 addressed this issue[bug 444931] and no longer sends a request.


• Opera does not do anything when an empty image src is encountered.

Why is this behavior bad?

1. Cripple your servers by sending a large amount of unexpected traffic, especially for pages that get millions of page views per day.


2. Waste server computing cycles generating a page that will never be viewed.


3. Possibly corrupt user data. If you are tracking state in the request, either by cookies or in another way, you have the possibility of destroying data. Even though the image request does not return an image, all of the headers are read and accepted by the browser, including all cookies. While the rest of the response is thrown away, the damage may already be done.

The root cause of this behavior is the way that URI resolution is performed in browsers. This behavior is defined in RFC 3986 - Uniform Resource Identifiers. When an empty string is encountered as a URI, it is considered a relative URI and is resolved according to the algorithm defined in section 5.2. This specific example, an empty string, is listed in section 5.4. Firefox, Safari, and Chrome are all resolving an empty string correctly per the specification, while Internet Explorer is resolving it incorrectly, apparently in line with an earlier version of the specification, RFC 2396 - Uniform Resource Identifiers (this was obsoleted by RFC 3986). So technically, the browsers are doing what they are supposed to do to resolve relative URIs. The problem is that in this context, the empty string is clearly unintentional.

HTML5 adds to the description of the tag's src attribute to instruct browsers not to make an additional request in section 4.8.2:

The src attribute must be present, and must contain a valid URL referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted. If the base URI of the element is the same as the document's address, then the src attribute's value must not be the empty string.

Hopefully, browsers will not have this problem in the future. Unfortunately, there is no such clause for <script src=""> and <link href="">. Maybe there is still time to make that adjustment to ensure browsers don't accidentally implement this behavior.

This rule was inspired by Yahoo!'s JavaScript guru Nicolas C. Zakas. For more information check out his article "Empty image src can destroy your site".

Source Link :http://developer.yahoo.com/performance/rules.html

Flash Player Runtime Errors and How to Fix Them

The following lists common runtime errors found with Flash Player and what you can do to fix them. Also available, Compiler Errors.

TypeError: Error #1009

TypeError: Error #1009: Cannot access a property or method of a null object reference.

This error occurs when you attempt to access a property or call a method (function) from an object variable that has no value (undefined) or has a null value. If the object is null, it has no value itself meaning it cannot contain any properties. The following example would be a situation where the error would occur:

var mySprite:Sprite; // null since not defined trace(mySprite.x); // Error #1009

Because the mySprite variable is null, accessing mySprite.x would be the same as null.x which is not possible, thereby creating the error condition. Note that this behavior is new to ActionScript 3.0. In ActionScript 2.0 and 1.0, doing this would cause a silent failure and return a value of undefined.

Usually when this error occurs, it means an error in your code logic. You're code is assuming an object exists when it does not. That is something you will have to identify and fix. This can sometimes be difficult because of the error's ambiguous text; it does not specify what specific object the error is in reference to. However, if you test a debug version of your project in your IDE, it will tell you.

Debugging in Adobe Flash Professional:

From the File menu, select Debug > Debug Movie.

Debugging in Adobe Flash Builder:

From the File menu, select Run > Debug [ProjectName].

When debugging (in either Flash Pro or Flash Builder), a Debug version of your project which will include more information about code execution that can help better identify errors. When the error occurs, code execution will pause and the line of code with the error will be pointed out in the code view. Additionally, the Variables panel can be used to inspect the values of the objects and properties within the current scope.

If there is a circumstance where it is known that an object may or may not exist, then you would first need to check to see if the object being used has a value before attempting to access properties or call methods from it. This can be handled through a simple if condition.

if (mySprite){  trace(mySprite.x); }

Alternatively, you can also encase your logic in a try-catch block, directly handling any error that may occur.

try {  trace(mySprite.x); }catch(err:Error){  // it's OK, we know mySprite may not exist }

Common circumstances where a #1009 may occur:

• root, stage, or loaderInfo is null. The root, stage, and loaderInfo properties of the DisplayObject class are unique in that their values are dictated by whether or not the DisplayObject is a child of the active display list. If the DisplayObject is not, these properties will each be null. They will not have valid values until the object made a child of the active display list throughaddChild or addChildAt. You can identify when this occurs using the Event.ADDED_TO_STAGE event.
  

  addEventListener(Event.ADDED_TO_STAGE, stageAndRootAndLoaderInfoAvailableHandler);

• A variable is declared, but not defined. As is the case with the mySprite examples, the mySprite variable was declared, so it exists, but it was never defined with a valid Sprite value. This can be common when creating new classes where you have correctly declared all of the necessary variable members but may have neglected to define them before they're being accessed.
• A timeline instance no longer exists. If you navigate to a frame within the timeline of a MovieClip that no longer has a timeline-placed object you're referencing in code, that object variable will be null. You will need to make sure you're on the correct frame or at least check to see if the object variable is still valid when used.

ReferenceError: Error #1056

ReferenceError: Error #1056: Cannot create property [property] on [Type]

This error occurs when you try to create a new variable on an object that does not already have that variable and is not allowed to have new variables created for it dynamically. Only instances of dynamic classes can have arbitrary variables defined for them. These classes include Object, Array, MovieClip, and a few others. Most classes, however, are not dynamic and limited to use only those variables which are part of their class's definition.

var mySprite:* = new Sprite(); // untyped to circumvent compiler errors mySprite.foo = "bar"; // Error #1056

The Sprite class is not dynamic so the variable mySprite above generates an error when an unrecognized variable foo is attempted to be set on it.

If you are in a situation where you need to set a variable in this manner, you have a couple of options. One option is creating a new class that extends the original and contains the property you need to use. For the case of mySprite above, a new class extending Sprite can be created to used in place of Sprite that contains the foo property.

// in CustomSprite.as package {  import flash.display.Sprite;  public class CustomSprite extends Sprite {   public var foo:String;   public function CustomSprite(){    super();   }  } }

var mySprite:CustomSprite = new CustomSprite(); mySprite.foo = "bar"; // OK

If you do not have control over the definition of the object you're working with, usually the best solution is making a hash map. A hash map (or simply map) will allow you to link a custom value with a unique key, or in this case an object, in a location other than within the object itself. Generic objects in ActionScript can map strings to values but for this to work - mapping values to object instances - a Dictionary instance will be needed for the map. Example:

var foo:Dictionary = new Dictionary(true); var mySprite:Sprite = new Sprite(); foo[mySprite] = "bar"; // OK

Here, you can see that instead of setting a property on the mySprite Sprite, mySprite is instead being used as a property on a fooDictionary (map). As long as you have access to both foo and the Sprite instance, you have access to custom values that are directly associated with that Sprite even though they are not defined on it. The nature of the map allows it to be used with any other objects as well, not just the mySprite instance. If at any time you need more custom variables, you would create a new map.

var foo:Dictionary = new Dictionary(true); var boo:Dictionary = new Dictionary(true);  var mySprite:Sprite = new Sprite(); foo[mySprite] = "bar"; // OK boo[mySprite] = "far"; // OK  var myMovieClip:MovieClip = new MovieClip(); foo[myMovieClip] = "none"; // OK boo[myMovieClip] = "away"; // OK

Hash maps are very versatile but they lack type safety and can be difficult or confusing to manage. When possible, it's recommended you use a custom class to solve this issue.

ArgumentError: Error #1063

ArgumentError: Error #1063: Argument count mismatch on [function](). Expected [#], got [#].

This occurs when a function is called in a way that does not satisfy the number of arguments that is expected for the function call. When a function is defined, it's parameters determine what arguments is expected to be passed into that function when the function is called. Unless given a default value, all parameters are required. Additionally, if a function has no parameters but arguments are provided when called (or more arguments than there are parameters are provided) this error will also occur. Examples:

function myAddFunction(a:Number, b:Number):Number {  return a + b; }  myAddFunction(1); // Error #1063 // exactly two arguments are required 

function myRandomFunction():Number {  return Math.floor( 10 * Math.random() ); }  myRandomFunction(1); // Error #1063 // exactly zero arguments are required

When function calls are made, the arguments used must match the parameters defined by the function definition. Note that this behavior is new to ActionScript 3.0. In ActionScript 2.0 and 1.0, doing this would cause a silent failure and the superfluous arguments would be ignored.

If you need to allow a function to be called with a varying number of arguments, you have two options: default parameters and the ...rest parameter. Default parameters specify optional parameters. Arguments may be passed into a function to satisfy these parameter values or they can be omitted at which point the default values will be used. To define default parameters, include an equals sign (=) with a default value next to the parameter in the function definition. All default parameters must be at the end of a parameters list; non-default parameters cannot be listed after a default parameter.

function myAddFunction(a:Number, b:Number = 0):Number {  return a + b; }  myAddFunction(1, 2); // standard use myAddFunction(1); // also OK, b will default to 0 myAddFunction(); // Error #1063, a is still required

The ...rest parameter signifies that any number of arguments can be used in place of where the ...rest is in the parameter list. Any required parameters before ...rest are still required. When using ...rest, any variable name may be used to signify the extra parameters. It must be preceded by 3 dots (.) and must not be followed by any additional parameters. In the function body, the ...rest variable references an array containing any arguments used in place of the ...rest parameter.

function myAddFunction(...values):Number {  var total:Number = 0;  var i:int, n:int = values.length;  for (i=0; i
Common circumstances where a #1009 may occur:
Event handlers. If you create a function that is used for an event handler, it must be able to accept single Event argument.
addEventListener(Event.ENTER_FRAME, enterFrame); function enterFrame():void {  // Error #1063, an event parameter is required! }
addEventListener(Event.ENTER_FRAME, enterFrame); function enterFrame(event:Event):void {  // Works! }
ArgumentError: Error #2025
ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
This occurs when you try to use a removeChild with a display object that does not exist within the parent object you are trying to remove it from. For example, in the following sample where myParent is a Sprite or some other DisplayObjectContainer instance that (supposedly) contains a child Sprite (or some other DisplayObject) called myChild:
myParent.removeChild(myChild);
this error would occur if the myParent instance (the "caller") did not contain myChild (the "supplied DisplayObject"). This could be because myChild was already removed prior to this call, or myChild exists within some other object. If this is happening when you think it shouldn't, try tracing the value of the child display object's parent to see if it's what you expect.
To be safe, when removing a child display object from its container, you should make sure the object you're removing it from is, in fact, it's parent.
if (myChild.parent == myParent) {  myParent.removeChild(myChild); }
This goes with the assumption that you need to explicitly remove that child from that specific parent. If you just want to remove the child from the display list, you can explicitly reference it's own parent through its own parent property rather than an object reference for the object you suspect might be its parent. In doing so, you should check to see that parent exists. If it's null, it is already off of the display list.
if (myChild.parent) {  myChild.parent.removeChild(myChild); }
This is the standard approach for removing an object from the display list. Verify it's on the display list (parent is not null) then remove the object from it's parent directly.
There is one exception to this rule: event handlers for the Event.REMOVED event when a timeline containing the child display object moves to a frame where the child does not exist. In this case, parent will be non-null but the removeChild will not work because the child display object is actually no longer on the display list. This circumstance would be extremely rare, but for absolute assurance that your code would continue without interference, you can attempt to handle the error in a try-catch block when attempting to remove the child display object with removeChild.

if (myChild.parent) {  try {   myChild.parent.removeChild(myChild);  }catch(err:Error){   // fail silently; child already removed  } }    

source link : http://www.senocular.com/flash/tutorials/runtimeerrors/

100 Popular jQuery Examples, Plugins and Tutorials

1. jQuery Lavalamp Menu – It is the jQuery plugin that is based of Guillermo Rauch plugins for mootools and Ganesh Mawwaha’s jQuery 1.1.x plugins. Through the Sliding Doors CSS/Javascript method, you are able to add a background hover effect on HTML link lists with Lavalamp by utilizing the Eazing library.

2. Superfish Menus – Suckerfish on ‘roids, This jQuery plugin allows the development of improved Suckerfish style of dropdown menus from the existing pure CSS type of dropdown menu. The features that are added as a result of these include: a timed-delay on mouseout, automatic utilization of hoverIntent plugin when present; obligatory IE6 –hover capability; animated sub-menu; accessibility through keyboard tab key; generation of arrows to indicate the submenus; use of drop shadows for browsers that are capable; and many others.

3. jQuery Context Menu – This jQuery plugin provides easy implementation, CSS styling, keyboard shortcuts and control methods.

4. Kwicks for jQuery – This highly versatile and customizable widget had started as just a port for Mootools framework.

5. jQuery iPod-style Drilldown Menu – jQuery has an iPod-style drilldown menu that helps users traverse hierarchical data with relative ease and control. This feature is very useful in organizing large data structures that don’t translate well into the traditional fly-out or dropdown menus.

6. jQuery File Tree – This jQuery plugin is a configurable AJAX file-browser plugin where you use to create a fully interactive and customized file tree as little as one of the Javascript code.

7. Recreate Mootools Home Page-Inspired Navigation Effect – Users of jQuery can recreate the same effects that you see in a Mootools.

8. CSS Sprites2 using jQuery – One can use jQuery to implement CSS Sprites2. One distinct advantage of jQuery over the other javascript libraries is that it allows users to select elements on a pages using CSS-like syntax that we are already familiar with.

9. jQuery Accordion – It is the jQuery plugin that allows the creation of the accordion menu. It can be used for nested lists, nested divs and definition lists. This plugin has options for structure specification, active element, when necessary, and animation customization.

IMAGE MANIPULATION

10. jQZoom – It is the jQuery plugin that easily allows the creation a small magnifier window near an image or group of images on the web page. You decide to build jQZoom to embed big images in your B2B. This creates the jQZoom in your eCommerce websites or any other websites.

11. jCrop – This jQuery plugin allows an easy and quick way of adding image-cropping functionality to web application. This functionality combines the use of typical plug in with a powerful cross-platform DHTML cropping engine that is compatible to common desktop graphics applications.

12. Captify 1.1.0 – It is a jQuery plugin that creates short and beautiful image captions that appear every time a user’s mouse passes over an image.

IMAGE GALLERIES AND VIEWERS

13. Simple Controls Gallery – This jQuery tools displays and rotates images by fading it into view over the previous images using navigation controls that pop up when the mouse moves over the gallery.

14. Agile Carousel – It is a jQuery plugin that provides for the easy creation of a custom carousel. This plugin makes use of PHP to call images from the folder that is specified by the user. Users can configure different options including slide timer length, controls, transition type, easing type and more.

TRANSITION EFFECTS

15. InnerFade – It is a small jQuery plugin used in the jQuery Javasrcipt Library. This plugin allows using fade effects on any element found within a container in and out. The elements may include divs, list items or images. In order to do this, you have to create your own slideshow and the produce a newsticker or an animation.

16. Easing Plugin – It is the jQuery plugin that comes from GSGD that provides advanced easing options. This plugin can support a default easing mode. This allows you to set your preferred animation once for all animations. It uses the Robert Penners easing equations for all the transitions.

17. HighlightFade – It is a jQuery plugin that allows the use of fading effects from one color to any other pre-selected colors at any transition speed and interval of color update using a color progression tactic that is customizable.

18. JQuery Cycle Plugin – It is a jQuery plugin that is classified as basic slideshow plugin. It is based on the Slideshow plugin by Matt Oakes, jqShuffle plugin by Benjamin Sterling and the InnerFade plugin by Torsten Baldes. This plugin can do auto-stop, before and after callbacks, pause-on-hover, and many other transition effects.

jQUERY CAROUSEL

19. Riding Carousels using jQuery – It is the jQuery plugin used for controlling items in a list in vertical or horizontal order. The list of items can be loaded with or without AJAX, or can be a static HTML content. It can be scrolled in either direction with or without animation effects.

COLOR PICKER

20. Farbtastic – It is a jQuery plugin that allows you to add more color picker widgets in a page using Javascript. These widgets are linked to an element and will update the value of that element when one particular color is picked.

21. jQuery Color Picker – It is a jQuery plugin that allows you to select color in a way that is almost the same as you pick colors in Adobe Photoshop. This jQuery plugin is a Flat mode element in a page and is easy to customize the look by simply changing the images. It also has powerful controls used for selecting the colors and fits easily into the viewport.

LIGHTBOX

22. jQuery ThickBox – It is a jQuery plugin that is created using the jQuery library. The function of this jQuery plugin is to resize images that are bigger than the browser window and provides versatility in inline content, images, AJAX content and iFramed content. It will remain at the center of the window even if you change the size of the browser window or you scroll the pages.

23. SimpleModal Demos – It is a jQuery plugin defined as lightweight plugin that creates a basic interface to provide a modal dialog. This jQuery plugin shall give developers a cross-browser overlay and a container that will contain data provided to SimpleModal

24. jQuery LightBox Plugin – It is a jQuery plugin that provide an option to present an image on a page in a simple and elegant manner. Under this jQuery plugin, the lightboxes can be assembled in one group and provides many options for configurations. It also provides both the manual and automatic options to create and to start lightboxes.

25. Revealing Photo Slider – This tool of jQuery allows to create a thumbnail photo gallery where clicking a button would reveal the entire photo and other information about the photo.

26. FancyBox – This jQuery tool automatically scales large images to fit in windows by adding a nice drop-shadow under the zoomed item. This tool can be used to group items that are related and add navigation between them. It is totally customizable through CSS and settings.

27. Facebox Image and Content Viewer – It is a lightweight plugin that displays images, divs and remote pages, through AJAX, inline on a page and on demand.

28. jQuery.popeye – It is a jQuery plugin that converts an unordered list of images into a simple image gallery. When an image is clicked, it enlarges just like with LightBox.

FORM ELEMENTS AND VALIDATION

29. jQuery Form Validation – It is a jQuery plugin that is fast, unobtrusive, scalable and easy to use validation plug in that offers a variety of methods for all types of validation needs. It comes from the very basic to the more complex schemes of validation.

30. Ajax Form Validation – This refers to the client aspect of validation using Javascript. The username will perform the validation by checking with the server whether a chosen username is available and valid.

31. jQuery AlphaNumeric – It is a jQuery plugin that uses javascript to allow you to control what characters a user can use and enter on text areas and text boxes.

32. jQuery.combobox – It is a jQuery plugin that provides a simple way of producing an HTML type of combobox from the existing HTML Select tags. This plug in was created to provide the solution on the limitation in styling of standard Select tag.

33. jQuery Checkbox – It is a jQuery plugin that creates a replacement for the standard checkbox. This plugin allows you to modify the look of the elements of the checkbox in the page.

34. File Style Plugin – It is a jQuery plugin that solves your problem with browsers that does let you style file inputs. This jQuery plugin also allows you to style filename field to normal textfield by using css.

35. Radio Button and Check Box Replacement – This tool of jQuery replaces the check boxes and radio buttons with a more attractive display.

36. Submit a Form Without Page Refresh – By using jQuery, you not only can add form validation to wordpress comments without any page reload but also submit your form without a page refresh.

37. jQuery AJAX Contact Form – Users of jQuery can make an AJAX contact form with a “honeypot” to foil email bots, load success and error messages without leaving the page and provides descriptive error messages detailing the reasons for the failed validation of the submitted value.

38. jQuery Form Validation – This form of jQuery can show form-input validators both the browser-side and server-side

STAR RATING

39. Simple Star Rating System – It is a jQuery plugin used for star rating system. This jQuery system was created with the basic framework of the star rating system of Wil Stuckey. This jQuery plugin provides the solution on the problem of the original script requiring too much coding. It also did away with the requirement for developing a star system.

40. Half Star Rating Plugin – It is a jQuery plugin that was developed in response to the clamor for an enhancement of the simple rating system of Ritesh Agrawal and allow for the use of half-star rating system.

TABLE PLUGINS

41. Table Sorter Plugin – It is a jQuery plugin that is used to turn a standard HTML table with TBODY and THEAD tags into a table which is sortable without resorting to page refreshes. This jQuery plugin can effectively sort and parse multiple data including data in a cell that are linked.

42. Autoscroll Plugin for jQuery – It is a jQuery plugin that provides for hotspot scrolling of webpages. This jQuery plugin will still work even with earlier versions of jQuery.

43. Scrollable HTML Table Plugin – It is a jQuery plugin that is used to convert HTML tables into scrollable tables. This jQuery plugin solution does not require any additional coding.

44. Table Row CheckBox Toggle – This jQuery tool adds a toggle function to any table row that you specify based on a CSS class name. This tool will toggle on by default any check boxes within that table row.

45. Tablesorter – This is a jQuery plugin that allows you to turn a standard HTML table with and tags to a sortable table without refreshing the page. This plugin can successfully parse and sort many kinds of data in a cell.

46. TableEditor – This tool allows flexible in-place editing of HTML tables. Users can easily drop handler functions to update.

ROUNDED CORNERS

47. jQuery Curvy Corners – It is a jQuery plugin that allows for the creation of nice looking rounded corners without the use of images. It is a jQuery plugin considered to be unobtrusive and can work well with all major browsers which include iPhone. Another nice feature about this jQuery plugin is that the corners to be rounded and its radius can be set easily.

OTHER JQUERY PLUGINS

48. HeatColor Plugin – It is a jQuery plugin that provides color to elements and determined by a value derived from that element. This derived value comes from a range of value which are either pre-designated or passed in. The element is then assigned a “heat” color which is derived from the position of the value within the range of values.

49. jQuery Date Picker – It is a jQuery plugin that is considered unobtrusive and clean. It adds date-entry functionality to web forms and pages. It was created from the basics up in order to attain flexibility and extensibility. It has varied options of use that allow you to all a calendar widgets to web pages and forms.

DYNAMIC CONTENT

50. Create a Log-in Form with jQuery – One can create a sliding panel that slides in to reveal new content and animate the height of the panel through jQuery.

51. Spoiler Revealer with jQuery – This is a technique in jQuery that can hide and reveal content with animation effect once it is clicked.

52. AJAX Upload – It is a jQuery plugin that provides for easy uploading of multiple files without having to refresh the page. This plugin also allows the use of any element to trigger the file selection window.

53. FCBKcomplete – jQuery also provides users with Facebook-like dynamic inputs along pre-added and auto-complete values.

54. Create Accessible Charts Using jQuery and Canvas – Users of jQuery can use the element to illustrate HTML table data. This technique makes data in a table accessible and while the chart is being shown for visual improvement.

MANIPULATING CONTENT

55. jQuery Books Widget – One can use jQuery with some custom Javascript to create interesting widgets like a browsable Amazon.com books widget.

56. Text Size Slider – Users of jQuery can control the text size of an article on a page using a slider. This feature of jQuery allows the user to control exactly the size they prefer and is a very impressive feature to have on a site.

57. Pagination – Users of jQuery can group large numbers of items into pages and present navigational elements that allow users to move easily from one page to another.

58. Coda-Slider – This jQuery tool also groups items together through navigational elements that allow users to traverse the pages.

59. Slick Auto-Playing Featured-Content Slider – This jQuery plugin allows users to cycle through panels and auto-playing different kinds of custom content. It features an arrow indicator to guide users on which panel he is currently viewing.

BROWSER TWEAKS

60. Setting Equal Heights with Query – Through jQuery, users can utilize a script that can equalize the box heights within the same container to create a tidy grid.

61. jQuery IE6 PNG Transparency Fix – This is a bug fix that uses jQuery selectors to automatically fix all PNG images in a page.

62. BGI Frame – This jQuery tool helps users in dealing with IE z-index issues.

63. Fix Overflow – This jQuery bug fix solves the issue on the scroll bar covering overflowing elements when the element is only one line.

64. Lazy Load – This tool can delay the loading of images below the fold on long pages, loading the images only when the user scrolls down on that part of the page.

65. Maxlength – This jQuery plugin automatically limits the number of characters a user can input in a field and giving feedback on how many spaces are remaining.

ANIMATION EFFECTS

66. Scrollable – It is a lightweight and flexible jQuery plug-in used to create a scrollable content. It can contain any HTML, including images, forms, text, video or a combination of any of them.

67. Fading Menu-Replacing Content – This jQuery tool lets users to utilize animation and change the way to style a page on-the-fly to react to events that happen on your page.

68. Build an Animated Cartoon Robot with jQuery – jQuery is able to provide an animation effect that simulates a faux 3-D animated background just like what are seen on scrolling video games.

TOP jQUERY TIPS

69. Prevent Animation Queue Build-up – Through jQuery, this natural queuing of animations is easy to code and user can move on to other important tasks

70. Rotate Through Tabbed Content – Through this functionality of jQuery, the movement is more likely to catch the user’s eyes, thus increasing the chances they will notice the tabbed box and allow the user to see all the content of the box instead of just the first tab.

71. Stopping the Rotation – This technique allows users to stop the rotating of tabs and stop it from switching when you are interacting with them. The technique involves some editing a couple of lines from the document ready function.

72. Build a Tabbed Content with CSS and jQuery – This technique outlines the steps required to easily customize to fit the size and color scheme, use fixed or variable height, automatically rotate through the tabs and stop the rotation when the user needs to.

73. Advanced CSS Accordion Effect – This technique is improved by the use of Javascript and all browsers will handle this technique even without JS enabled.

74. Consistent Base Font Size – This is the best jQuery technique to gain control over your font sizes until IE finally support the resizing of text in pixels.

75. Maintain Consistent Margins – This jQuery technique enables users to remove the margin and padding from every element instead of CSS resets.

76. Set a Float to Clear a Float – This jQuery is one of the most important things to understand with CSS. However, it is also important to learn how to clear floats.

77. Image Replacement – This image replacement technique involves the positioning an image over the top of the HTML. One feature of this technique is that even when images are disabled, the text is still visible.

78. Faux Columns – This technique allows 2 adjacent columns with unequal amounts of content to have 1px tall background image being repeated vertically in the containing element of the 2 columns.

79. Animate a Hover with jQuery – This technique allows users to animate an image while hovering over it and allow users to see information while doing that

80. Background Image Animation Using jQuery – This technique involves producing animation effects by changing the position of the background image.

81. Animated Menu using jQuery – This technique involves the use of animated menu using CSS, XHTML and javascript.

82. Create an Animated Navigation with CSS and jQuery – This technique provides for the creation of a cool navigation enhanced with animation effect and visual feedback.

83. Load in and Animate Content with jQuery – This technique uses AJAX functionality so that the content loads into the relevant container instead of having to navigate to another page.

84. Implementing Prototype’s Array Methods in jQuery – This technique gives a particular array all the methods that Prototype adds to their Array and Enumerable objects.

85. 43,439 Reasons to Use Append() Correctly – This technique provides for the proper way of using this jQuery method. Although an extremely easy and useful method to work with, it can significantly affect the performance of the page.

86. Collapsible Content Using jQuery – This technique provides the steps in having the content collapsible through simple jQuery codes.

87. Minimize Manipulation of DOM – We can further make the code faster if we cut down on the frequency that we insert into the DOM. Insertion operations of DOM will make things slow down.

88. Give context to your selectors – When you use the selector, the entire DOM will be traversed as a result of the action. This can be a very expensive process.

jQUERY TUTORIALS

89. How jQuery Works – This is a featured tutorial on jQuery by John Resig, the creator of jQuery. This is an ideal basic tutorial for those who are starting to learn jQuery for the first time.

90. jQuery in 15 Days – This is a 15 day tutorial that turns you from a greenhorn to an expert in 15 days.

91. Bassistance – This tutorial covers the basics of jQuery up to the more advanced topic like building plugins.

92. Remy Sharp’s Blog – He has written numerous tutorials and plugins and he is also the person responsible for the very helpful jQueryForDesigners website which also provides useful tutorials in answer to request of readers.

93. CSS Tricks – This reference site is full of examples, tips, tricks, tutorials and news about cascading style sheets (CSS).

94. jQuery Cheat Sheets – It provides to aspects of cheat sheets. These are: those made for iPod and other mobile devices; and those with the A4 cheat sheet.

95. How to Build jQuery Plugins – One can try any of the following tutorials: A Plugin Development Pattern; Developing a jQuery Plugin; and Building your First jQuery Plugin.

96. jQuery Pop-up Menu Tutorial – This is a tutorial material that focuses on pop-up link menu.

97. The jSkinny on jQuery – It is a tutorial that covers jQuery javascript library.

98. How to Get Anything You Want – This is an introductory tutorial on traversal methods and jQuery selectors and their use in DOM navigation

99. It’s all about CSS – As the title suggests, this tutorial is all about CSS selectors. Once you learn from this tutorial, you can now easily query the DOM.

100. jQuery Crash Course – This tutorial is designed for web designers with advanced knowledge of codes.

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