Yahoo! User Interface Library (YUI)

The Yahoo! User Interface Library (YUI Library) is a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX. The YUI Library also includes several core CSS resources. All components in the YUI Library have been released as open source under a BSD license and are free for all uses that permits both commercial and non-profit use.

The Yahoo User Interface (YUI) Library is a coherent collection of JavaScript and CSS resources that make it easier to build richly interactive applications in web browsers. Some pieces of YUI, like the Event Utility, operate under the hood and are simply there to make in-browser programming easier. Others, like the Calendar Control, comprise visual widgets that can be placed on your page with a default look-and-feel. YUI supports the vast majority of browsers that are in general use.

YUI is backed by developers at Yahoo!, increasingly comprehensive, well-documented, and supported by a growing community in the YUI forums. You can download the distribution directly (latest version on the time this blog being written is 2.4.1) from YUI download at Yahoo Developer site. Full API documentation is available from here. Get examples (more than 230) from YUI examples page. Also keep yourself updated by subscribing to YUI Blog. Also visit "Skinning YUI", a good article on making YUI components look and feel better and fitted well with your site design.

This post is summarized from official YUI site.