What firefox extensions do you use for web design/development? Although not all of mine are strictly related to this, most of them are:

* Colorzilla - grab the colour code of anything on any website
* MeasureIt - measure sizes and distances on any website
* Web Developer - toolbar giving hundreds of tools for website development
* eBay Negs - open all the negative comments that an eBayer has received in one list
* Search Status - Google PageRank and Alexa Rank in one place
* FireFTP - use FireFox as an FTP program
* Linky - open all highlighted links in new tabs
* AdSense Notifier - keep track of your AdSense income
* Word Count - count all the words in a highlighted paragraph
* Colour Contrast Analyser - check that colour schemes meet legal requirements
* IE Tab - open something in Internet Explorer without leaving FireFox
* GreaseMonkey - heaps more extensions, the best one being having the latest Dilbert cartoon show on the Google index page!

There's also the web developer toolbar which is fantastic in every way!

I don't load my browser down with a whole lot of extentions.