JQuery

jQuery - a Powerful Cross Browser JavaScript Library
jQuery is a fast and concise, cross browser JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax for rapid web development.

Benefits of jQuery

 * 1) Cross Browser - jQuery is designed to work on all modern browsers, which eliminates the need to create extra code and hacks for different browsers.
 * 2) Concise - jQuery will cut your JavaScript code to a fraction.
 * 3) Eclectic Plug in Library - jQuery is one of the most popular JavaScript frameworks and has perhaps the largest plug in in library.
 * 4) Lightweight - jQuery leaves a small footprint compared to the functionality it adds,  jQuery is also available via CDN from companies such as Google (http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js)  and Microsoft (http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.js)