Web Developer Tools You Can't Live Without: Firefox Extensions

I just wanted to take a few minutes to briefly talk about two extremely useful web developer tools -- more specifically, two browser extensions for Mozilla Firefox.

1. Web Developer (toolbar) - this is, hands-down, the most useful Firefox extension for web developers/designers. Definitely a tool you should not be without.
   
   Download link: https://addons.mozilla.org/en-US/firefox/addon/60
   Author: Chris Pederick
   Author's website: http://chrispederick.com/work/web-developer/
2. SearchStatus - An excerpt from the author's website explains it better than I could: "SearchStatus is a toolbar extension for Firefox and Mozilla that allows you to see how any and every website in the world is performing. Designed for the highly specialized needs of search engine marketers, this toolbar provides extensive search-related information about a site, all conveniently displayed in one discreet and compact toolbar." -- The bottom line is...YOU SHOULD BE USING THIS. (subtle, I know.)
   
   Download link: https://addons.mozilla.org/en-US/firefox/addon/321
   Author: Quirk (company name)
   Author's website: http://www.quirk.biz/searchstatus/
   
   Do you have another web developer tool that you just can't live without? Tell us about it in a comment!