Sematopia.com has post a quick and easy tutorial on learning Ajax in 20 minutes. They have stated that this tutorial only works in Firefox so if you are an IE user you need to add some Javascript to detect which XMLHTTP object to select.

Here is a quick overview and example of AJAX in action. Before you begin, this example will only work in FireFox. You’ll have to change few things in the JavaScript for it to work in IE. To download the files used below click here. If you don’t have PHP/Apache installed, follow the tutorial I made to install it. The example below assumes you know the basics of PHP, you can learn as you go along if you don’t. A good reference is the base PHP website.

Read the whole tutorial here