The Web Developer extension for Firefox is an invaluable tool when you are writing JavaScript that dynamically changes the HTML on a Web page. The feature I use most often is:

Web Developer > View Source > View Generated Source

This shows you the HTML as it is at this moment in time, rather than the original HTML that came down the pipe.

The trick for IE is to paste the following line of code in it's entirety into the address bar and voila!

javascript:void(window.open("javascript:document.open(\"text/plain\");
document.write(opener.document.body.parentNode.outerHTML)"))

Good stuff!!!