DOMSpy (formerly HTML Tweak) This is a cool tool that someone I worked with stumbled across a few years ago. I'm glad I remembered the company, as it appears the name of the product has changed since I last used it. I believe it used to be called HTML Tweak. Now it's DOMSpy.

http://www.dubbeldam.com/DOMSpy.html

This thing lets you spy on something in an IE window and easily navigate to the HTML beneath it all so you can see what's going on (and why it doesn't look like you expected). You can even mess with some settings right there and see your changes.  ¶ 8:27 AM