If your head wasnt in the sand during 2005, youve probably heard of AJAX (Asynchronous JavaScript and XML). Just in case youre wiping the sand out of your hair right now, heres a brief overview. AJAX is a rebranding of technologies introduced in Microsoft Internet Explorer (IE) several years ago. These technologies, branded by Microsoft as Dynamic HTML (DHTML) include HTML, an implementation of Cascading Style Sheets (CSS), plus the ability to manipulate a page with JavaScript through the browsers Document Object Model (DOM).
IE 5.0 quietly introduced something quite innovative (if proprietary): an ActiveX object called XmlHttpRequest. This object allows developers to write JavaScript code that communicates asynchronously back to the server, retrieves a response, and then dynamically updates the display without requiring a full-page refresh. Since updating part of a page is faster than updating all of it, applications appear much more responsive. (Note that you can dynamically manipulate the page with JavaScript even if you dont talk to the server first.) With AJAX, Web applications can behave more like their desktop counterparts using a Web browser (no special software or plug-ins are required).
