22 Add-ons in this Collection
Firebug by Joe Hewitt, Jan Odvarko, others
Greasemonkey by Anthony Lieuallen, Aaron Boodman, others
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.
The Web Developer extension adds various web developer tools to the browser.
Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on...
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
A customizable mouse gestures extension which enables to execute various commands and user scripts with six types of gestures.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Show the IP address of the current page in the status bar. It also allows querying custom information services by IP (right click) and see location and avaiable vouchers for shopping sites. Additionally you can copy the IP address to the clipboard.
Firebug extension to view which CSS rules are actually used.
Easy cache status & management from status...
Pixel Perfect by Mike Buckley, Lorne Markham, others
Pixel Perfect is a Firefox extension that allows web developers and designers to easily overlay a web composition with semi-transparent layers (images). These layers can be consequently used for per pixel comparison between the page and a layer.