just in case this is useful for us: http://javascriptly.com/2008/08/yui-30-changes-from-the-root/ " 5 goals: • Lighter (less K-weight on the wire and on the page for most uses) • faster (fewer http requests, less code to write and compile, more efficient code) • more consistent (common naming, event signatures, and widget APIs throughout the library) • more powerful (do more with less implementation code) • more securable (safer and easier to expose to multiple developers working in the same environment; easier to run under systems likeCaja or ADsafe) [...] So, what’s new in YUI 3.0? Many things, both large and small like: • Intelligent loading. YUI detect which modules it needs to load, and then download them from a server — it will also join the modules’ JavaScript source files together, in order to optimize download time. • Change to a “YUI” namespace instead of “Yahoo” namespace in YUI 2.x branches. • Combine DOM events with custom events, making it possible to work with all events in a unified way. • Borrow “selectors” idea from JQuery to allow finding and working with nodes on an individual and group basis. • Chaining - another JQuery’s idea that makes it possible to write more compressed chaining syntax in implementation code. " Thanks -Vincent