Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Visual bookmarks for Firefox. (Works with all latest versions of Firefox)
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 Online HTML 5 validation, you need 0.962
Lets you load pages in IE with a single right-click, or mark certain sites to *always* load in IE.
A simple, clean and easy-to-use FREE Firefox extension for video download and Flash download. Supports Windows/Mac/Linux operating systems and the latest Mozilla Firefox. Now Supports Mozilla Firefox 4 and English, Spanish, Chinese language.
Add "Go Parent Folder" menu to context menu in The Library list view and Search result in Bookmarks Sidebar.
Tab grouping, vertical tab tree, multi-rows, and various tweaks for power users.