The best security you can get in a web browser!
Allow active content to run only from sites you trust, and protect yourself against XSS and Clickjacking attacks.
The Web Developer extension adds various web developer tools to the browser.
Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager.
View HTTP headers of a page and while browsing.
Add, modify and filter the HTTP request headers sent to web servers. This addon is particularly useful for Mobile web development, HTTP testing and privacy.
Adds links to convert and download Youtube, MyVideo, Clipfish, Sevenload, Dailymotion, MySpace videos as MP3 files. Visit our site: http://www.video2mp3.net for more information
Make any pages' search functionality available in the Search Bar (or "search box")...
Control what gets sent as the HTTP Referer on a per-site basis.
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)
CodeBurner is a Firefox add-on that integrates with Firebug, to extend it with reference material for HTML and CSS.
Useful tools for the nightly tester.
Collections are groups of related add-ons that anyone can create and share.Explore Collections