The best firefox addons for web development

There are lots of firefox addons for web development; here are the best firefox addons for web development I use on a daily basis.

firebug
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

ySlow
YSlow analyzes web pages and why they’re slow based on Yahoo!’s rules for high performance web sites.

google pagespeed
Page Speed is an open-source project started at Google to help developers optimize their web pages by applying web performance best practices. Page Speed started as an open-source Firefox/Firebug add-on and is now deployed in third-party products

total validator
Perform multiple validations and take screen shots in one go. This 4-in-1 validator works with external, internal, or local web pages using a local copy of the desktop tool obtained from
totalvalidator.com
flagfox
Displays a country flag depicting the location of the current website’s server and provides a multitude of tools such as site safety checks, whois, translation, similar sites, validation, URL shortening, and more…

live http headers
View HTTP headers of a page and while browsing.

screengrab
t will capture what you can see in the window, the entire page, just a selection, a particular frame… basically it saves webpages as images – either to a file, or to the clipboard. It captures Flash too!

useragent switcher
adds a menu and a toolbar button to switch the user agent of firefox

the list is a very small selection of the web development addons available, but it contains the addons that I use every day. if there are any others that you can suggest, please comment and ill try them out =)