Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
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.
A customizable mouse gestures extension which enables to execute various commands and user scripts with six types of gestures.
Note: If you are encountering the Connecting... problem see instructions below.
The updated, fully supported IE Tab. Embed IE in a Firefox tab. IE Tab Features: FF 4+ support, IE 7-9 compatibility modes, old IE Tab settings import.
Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.
Use PDF Download to do whatever you like with PDF files on the Web. Regain control and eliminate browser problems, view PDFs directly in Firefox as HTML, and use the all-new Web-to-PDF toolbar to save and share Web pages as high-quality PDF files.
Status bar widgets and progress indicators for Firefox 4+
Make any pages' search functionality available in the Search Bar (or "search box")...
Help make Firefox better. The Add-on Compatibility Reporter enables you to report if the Firefox add-ons that you're using are working properly.
Color tools for web development.
Color picker and eyedropper + saving colors and trying out colors with drag and drop.
This 15KB restartless add-on will add a "File" -> "Restart" menu item and a ctrl/cmd + alt + r hotkey to restart Firefox or Seamonkey.
Open Bookmarks/History/Homepage/URL/Search in new tabs, and more utilities for tabbed browsing, including Protect/Lock/Faviconize/Unload Tab, Reload Every, Select and manipulate multiple tabs simultaneously, Tab Stacking/Coloring, etc.