Highly visited sites like Facebook.com, Twitter.com, Myspace.com, Google.com heavily use this technology. They shows their content without reloading their script.
In 1990 the web browser was able to show only the static HTML pages. In 1996 the internet explorer was able to load Asynchronous data with iframe. Latter time Mozilla, opera supported AJAX through HTML HTTP request objects.
First time the idea of AJAX came out was by Jesse James Garrett.
- AJAX is a combination of java script and XML.
- HTML, XHTML or CSS are used to represent the data with style.
- Document object model is used to show the data dynamically.
- XML is used to interchange the data with server. XSTL is used as supporting matter of XML.
- XML Http Request is used to send final request to server and its an interesting operation.
- As it is fully dynamic language, sometime all of the functions can not be represented correctly in the HTML.
- AJAX creates the HTML pages dynamically. For that reason when we are browsing sites we can not go back to the previous page as it was made dynamically. The back button does not work there.
- The url links are ended with a ( hash #) for that reason we can not book mark this sites as our need.
- Search Engine robots never follows the Java script. So that if you code something with AJAX it will not have a SEO value to SEO robots.
- Some of the device do not support AJAX like PDA and mobile phone. This page can not run AJAX script.
- As AJAX continuously send request to server, you need to have good support and web server to run AJAX script.