This is a listing for top 10 necessary – Must Have – Firefox extensions for webmasters, and even every Internet user.
SEO for Firefox : Aaron Walls great extension which shows you every seo statistic within a Google Search.
Download Embedded : With this tool you can download embedded files like flash movies (youtube) and pretty much any embedded content.
LiveHTTPHeaders : Find out what all is going on with your web browser.
ColorZilla : allows you to pull colors off a page.
Firebug : Awesome for debugging html/css and even profiling your page finding out what is making it hang.
Google Global : From PPC expert at Redflymarketing this handy tool lets you see Google results from various countries.
Inbound Link Quality Extension : An interesting SEO tool which gives you ranking based on inbound links and their authority.
SEO Link Analysis Script : Link verification and deep analysis.
SearchStatus : One of the most used. Shows alexa/compete/pagerank. Useful for quick stats.
Web Developer : This is a must have for any web developer. Lets you edit and view css on the fly and also apply different stylesheets to different pages.
