Anyone used this little tool yet? I learned about it in a Dr. Dobbs article this month by the author, Joe Hewitt. It's a plug-in for Firefox that provides a bunch of tools for web developers. Too much, really, to list here, but if you're an ASP.Net dev think of IE dev toolbar + fiddler + javascript debugging + css profiling + a bunch more. You can basically peel a page like an onion, no matter how complicated.
http://www.getfirebug.com/
http://www.getfirebug.com/