Earlier I discussed Web-based Desktop Interfaces which do lots of various tricks in lots of various ways to provide a consistent (at least with respect to computer users') user experience. How do they do that you ask?
The same developers also produce Bindows, which is a full, desktop type set of user interface elements usable to create an entire application interface. It's a little on the expensive side for a commercial license. However, doing these elements on your own dev time, and making them fast and cross-browser compatible is not going to be easy.