AJAX

A very good overview about ajax was presented by steffen meschkat.
He works in the team of google maps

Ajax is the acronym for Asynchronous Javascript and XML.
It is not new. It is a kind of DHTML which had its hype a few years ago.
If you use Yahoo, Google and Websites like Flickr, you certainly have noticed Ajax in form of a graphical user interface quite similar to the windows, linux or osx desktop.
Regarding the web based email clients of yahoo and google, you will notice that they are easier to operate for the users. The operation is faster and more userfriendly than a year before.
The technique behind consists of HTML, CSS, XML, XSLT and JavaScript. It is amazing to see, how these techniques get more and more popular.