As part of my research at the University of Washington, I've been working on a new web-based JavaScript/HTML/CSS editor that helps you find bugs as you type:
http://faculty.washington.edu/ajko/projects/cleanroom/
If you try it, and succeed at finishing the task described on the page above, I'll send you a $10 Amazon gift certificate. Because I'm doing this to evaluate the editor, you'll be randomly assigned one of two different versions of the tool.
Because it's a research prototype, it's still a bit clunky and slow, but I think you'll find it interesting to see how future code editors might work.
(The editor is based on several open source technologies, including Bespin, JSLint, and ANTLR, along with my own technology.)
Thanks!
Andy Ko
Assistant Professor
The Information School
University of Washington