The Web Developer extension adds various web developer tools to the browser.
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox...
Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon
For Firefox 23+, you need 0.958 (under review)
Dust-Me Selectors is development tool that scans your website to find unused CSS selectors.
Inline Code Finder is an add-on to Firebug, to be able to find HTML elements with any of the below issues:
* Inline style
Detailed description can be found athttp://www.robertnyman.com/inli...
AutoAuth automatically submits HTTP authentication dialogs when you’ve chosen to have the browser save your login information.
Looks for broken links on page, links that are not working anymore - returning 404 code.
You can select to check whole page, or just links in selection.
You can check anchors, options, area tags.
Is incredible fast and lightweight !