This is a ground-up redesign of YUI:

1. Selector-driven: YUI 3 is built around one of the lightest, fastest selector engines available, bringing the expressive power of the CSS selector specification into actions that target DOM nodes.
2. Syntactically terse: Without polluting the global namespace, YUI 3 supports a more terse coding style in which more can be accomplished with less code.
3. Self-completing: YUI 3’s light (6.2KB gzipped) seed file can serve as the starting point for any implementation. As long as this seed file is present on the page, you can load any module in the library on the fly. And all modules brought into the page via the built-in loader are done so via combo-handled, non-blocking HTTP requests. This makes loading the library safe, easy and fast.
4. Sandboxed: YUI modules are bound to YUI instances when you use() them; this protects you against changes that might happen later in the page’s lifecycle. (In other words, if someone blows away a module you’re using after you’ve created your YUI instance, your code won’t be affected.)

It’s especially nice to see the new terse YUI namespacing, so you can just type YUI() instead of the older longer syntax.

The cool thing about YUI (and this release) is that it is literally driving the Yahoo! Home Page. That’s pretty awesome of Yahoo! to release this code and make it generally available to the wider community. Congrats to the whole YUI team on the new release.

Guys from ExtJS publishe an excellent article about understanding principles of Drag & Drop.

One of the most powerful interaction design patterns available to developers is “Drag and Drop.” We utilize Drag and Drop without really giving it much thought – especially when its done right. Here are 5 easy steps to ensure an elegant implementation.