If you are a web developer and you use Firefox for your browsing/testing/debugging/CSS needs you HAVE to get these tools:
Anytime I’m on anyone else’s computer now I miss these tools dearly. You really get spoiled. Oh and did I mention they’re completely FREE?
Web developer extensions lets you edit both CSS and HTML in real time so you can tweak things live on a page. It also comes with a million other really useful features like a ruler, validation, speed test, ability to see and dissect every type of element – forms, images, divs, etc, etc. Way too much to get into here, but I’ll say this: spend a few hours exploring all the options and you’ll be amazed at how much it lets you do – it will really cut your development/debugging time in half.
Instead of trying to go over all the features, just check them out for yourself: