Ajax – New approach for creating Web Application

From wikipeida, Asynchronous JavaScript and XML (Ajax) is a web development technique for creating interactive web applications using a combination of: techniques. It is not a technology in itself, but a term that refers to the use of a group of technologies together:

1. XHTML (or HTML) and CSS for presenting information
2. The Document Object Model manipulated through JavaScript to dynamically display and interact with the information presented
3. The XMLHttpRequest object to exchange data asynchronously with the web server.

Advantages:

1. data can be manipulated without having to render the entire page again in the web browser
2. allows web applications to respond more quickly to many types of user interaction
3. avoid repeatedly sending unchanged information across the network
   – save bandwidth and improve speed of loading the page
4. no browser plug-in is required for Ajax, it requires users to have JavaScript enabled in their browsers.
5. because Ajax applications are built using nothing more than current web standards, they are relatively easy to create.
6. freedom from the Page Refresh
7. instant field Checking & Saving
8. Single Screen Interface

Limitation:

1. Major con is some browsers do not support JavaScript or ActiveX. Security settings might cause even Internet Explorer to not support Ajax (ex: JavaScript might be disabled).
2. break the expected behavior of the browser's back button, undo their last change
3. difficult for a user to bookmark a particular state of the application
4. without clear feedback to the user [1], smart preloading of data [2], and proper handling of the XMLHttpRequest object [3] users might experience delay in the interface of the web application
5. provides many challenges for developers interested in adhering to Web Accessibility Initiative (WAI) accessibility guidelines
   -Solution: provide content only to specific portions of a web page, Non-Ajax users would optimally continue to load and manipulate the whole page as a fallback

Conclusion:
Ajax: a Solid Alternative:

By allowing more sophisticated functionality using easier-to-implement web standards, Ajax is proving a real alternative for creating powerful web applications.

Reference:
1. Ajax: The New Web Interface Design Development Approach Everyone Talks About

2. Wikipedia

3. Using Ajax for Creating Web Applications

4. Andy's Bookmark

Checklist of Checkpoints for Web Content Accessibility Guidelines 1.0

W3C has summarized Web Content Accessibility Guidelines 1.0 into a Checklist with priorities.

It saves our time in reading all the content of the guideline line by line. Moreover, it has categorized all the points according to their importance. If we got enough time, we can check all of them, otherwise, we can have a clear priority to check those important one first.

There are THREE priorities:
Priority 1: this is a basic requirement for most people to access our site.
E.g. provide text equivalent for non-text elements

Priority 2: this can remove most barriers to access our site.
E.g. ensure foreground and background provide sufficient contrast so that even people with color deficit can view it.

Priority 3: this can further improve the access to our site.
E.g. specify the expansion of the abbreviation when it first appear

For more details, you can visit:
http://www.w3.org/TR/WCAG10/full-checklist.html