Enterprise Java Technologies Tech Tips: "AJAX stands for Asynchronous JavaScript and XML. In essence, AJAX is an efficient way for a web application to handle user interactions with a web page -- a way that reduces the need to do a page refresh or full page reload for every user interaction. This enables rich behavior (similar to that of a desktop application or plugin-based web application) using a browser. AJAX interactions are handled asynchronously in the background. As this happens, a user can continue working with the page. AJAX Interactions are initiated by the JavaScript in the web page. When the AJAX interaction is complete, JavaScript updates the HTML source of the page. The changes are made immediately without requiring a page refresh. AJAX interactions can be used to do things such as validate form entries (while the user is entering them) using server-side logic, retrieve detailed data from the server, dynamically update data on a page, and submit partial forms from the page.

What is particularly attractive about this is that AJAX applications do not require a separate plug-in, and are platform and browser-neutral. That said, AJAX is not supported as well in older browsers. Care needs to be taken in writing client-side script that accounts for the differences between browsers. You might consider using a JavaScript library that abstracts the browser differences and in some cases support older browsers using alternative interaction techniques. For more details, see the AJAX FAQ for the Java"