Web Developer Extension on chrispederick.com: I hereby declare this to be the greatest Firebird plugin ever.
Ever wanted to reverse engineer a form submission using POST? Tough to do because the form data is based in the body of the request instead of the URL or the headers. This toolbar has an option to simply convert all the forms with POST to GET. The form will likely break when submitted, but at least you can examine the URL to see what’s in there.
You can outline block-level elements (any element you choose, really). Highlight images without ALT text. Validate every type of data available. View inline information about CSS IDs and Classes and form elements. Resize the window to 640 x 480 or 800 x 600 to check layout.
Great, great tool. Firebird rules.