My Firefox Plug-ins
Here is a list of the best Firefox plug-ins for web developers.
Anyway, these are the plug-ins I use.
Category: Web Developer Plug-ins
Firebug – Essential
Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page…
https://addons.mozilla.org/de/firefox/addon/1843
And here a list of the best firebug extensions:
-
Firequery
– a firebug extension for jQuery dudes:

http://firequery.binaryage.com/ -
YSlow
for web performance and speed freaks

http://developer.yahoo.com/yslow/ -
Pixel perfect
– for exactly perfect PSD to HTML checking

http://www.pixelperfectplugin.com/ -
FirePHP
– php to firebug console logging

http://www.firephp.org/ -
Google Page Speed
– from the YSlow genius who is now at Google.

http://code.google.com/speed/page-speed/ -
Code Burner
– HTML & CSS reference

http://tools.sitepoint.com/codeburner/ -
FireRainbow
– Yay- Syntax highlighting in firebug.

http://firerainbow.binaryage.com/ -
FireCookie
– why not look at your cookies from within firebug?

http://www.softwareishard.com/blog/firecookie/ -
LiveCoder
– take a look at the internal state of firefoy thingys.

http://getlivecoder.com/ -
Firediff
– watch things change at run time.

http://www.incaseofstairs.com/firediff/
Web Developer Toolbar
A great tool.
http://chrispederick.com/work/web-developer/
Measure It
A cool little screen measuring tool.
http://www.kevinfreitas.net/extensions/measureit/
HTTP Fox
Keep an eye on traffic.
http://code.google.com/p/httpfox/
Live HTTP Headers
Heads up!
http://livehttpheaders.mozdev.org/
Json Viewer
A great idea, syntax highlight json from within Firefox!
http://brh.numbera.com/software/jsonview/
Color Zilla
RGB, Hex, Eyedroper, Color Picker…
http://www.colorzilla.com/firefox/
Tamper Data
Fuzz the web server / http data stream
User Agent Switcher
Give Firefox a true identity crisis.
http://chrispederick.com/work/user-agent-switcher/
IE Tab
Whoa – more split personality issues. Render pages using MSIE within Firefox, and switch between rendering engines quickly.
Screengrab
The best in-browser shotter.
iMacros
Record and play like it’s Windows 3.1 for workgroups.
http://www.iopus.com/imacros/firefox/?ref=fxmoz
Selenium
Most powerful GUI testing framework.
Total Validator
Get the joy of compliant and valid source code.
http://www.totalvalidator.com/tool/extension.html
Dummy Lipsum
When writer’s cramp sets in, still make your daily page quota.
http://sogame.awardspace.com/dummylipsum/
Grid Fox
For all you subtraction lovers.
http://www.puidokas.com/portfolio/gridfox/
XML Developer
Transform, rotate.