Firebug

Firebug is a life saver when it comes to web development -- from introspecting your CSS to digging up details on AJAX calls, Firebug is there to help see what's going on under the covers.

This is one of the gems on my system. Whenever you have to create some AJAX interfaces, this tool comes in and supports you where ever you want. No matter if it is simple JavaScript debugging (with breakpoints) or stuff like modifying css, html or checking what messages have been send between browser and server. I love it ;)

This is a must have tool if you are doing anything from CSS + HTML to AJAX and security auditing.

This tool comes straight from heaven. They can take every tool away from me except firebug and vim. If they do that i am going on a strike.

Fire bug is a great Tool...

It helps me to understand how Comet and Polling are different in architecture and performance
[Read Hacking Gmail and Meebo]

I don't know how the web developers before Firebug did the things that did.... i just imagine a very hard and blind work! Firebug is the best tool!

Now that I teach high school students how to write webapps with AJAX, I see it wouldn't be possible without firebug.

I cry thinking about the years of web development I have done (and wasted) without firebug.

I agree, this tool is straight from the divine...

great tool for developing css on a website! :)

Its easy to use and almost without any bugs

It's quite good but... WebKit's built-in inspector is much better :)