Firefox 3.5 Rated 5 out of 5 stars

You can make it compatible with the Nightly tester tools add on.
https://addons.mozilla.org/en-US/firefox/addon/6543

This review is for a previous version of the add-on (1.2.2). 

New Version - 1.3

New version (1.3) in https://addons.mozilla.org/en-US/firefox/addons/versions/5459.