For CSS Code USED
CSS validator – This tool provide you to Check the validity of CSS code of your web page. It's open the results in the new tab.
CSSMate – It used for firefox extension for edit CSS files. it's make the code easy for understand and separte in different sheets.
Aardvark – It is useful add-ons in Firefox useful for web developers and designers. It's provide you to view CSS attributes, id, class by highlighting page element individually.
IE Tab - It is another extension for the firefox. This is helpful for the designers for view their CSS projects on Internet Explorer withing Firefox.
EditCSS –It's helps the web developers to edit and modify currently loaded style sheets and displays the code into a sidebar of Mozilla Firefox
Style Sheet Chooser II - it's allows you to choose author-provided alternate style sheets for a web site.
Debugging and Analysis
Load Time Analyzer – The Load Time Analyzer allows developers to measure and graph how long web pages take to load in Firefox. The graphs display events like page requests, images, stylesheets and scripts etc.
DOM Inspector: DOM (Document Object Model) it's inspect the structure and properties of the window and it's contents.
HTML Validator – This extension used to validate web pages with HTML standards of W3C. It's help to show the erros.
YSlow - It's awesome tool that analyzes your web pages, Why it's slowing down while loading and check the performance of the Web sites.
Pixel Perfect: Pixel Perfect is a Firefox/Firebug extension that allows web developers and designers to easily overlay a web composition over top of the developed HTML.
ColorZilla – It's help the developers for selecting the Advanced Eyedropper, Color Picker, Palette Viewer and other colorful goodies for your Firefox.
FirePHP – Identify the PHP code used in the code and display on this extension.
Greasemonkey – it is used withing the Firefox and allow you to customize the java script or any webpage aspects or it's functions.
TestGen4Web – This is interesting extension that records your ongoing activities and store it. It's play on your demand.
View Source Chart – It's shown you any webpage Source code.
Web Developer – The Web Developer extension adds a menu and a toolbar with various web developer tools.
X-Ray – it allows users to view webpage code with a right-click and see how document was constructed.
Measureit – Calculate the measurement is difficult task for each developers. This extension help you measures the specifications of tables, paragraphs on internet.
Poster – This extension help for developers to interacting with web services and other resources in the web content.
Clipmarks – it's help you to save any part of web page like blog posts, articles even you can post directly to the twitter or facebook or share to any one.
Codetech – Edit your documents withing the Firefox and feel like the Dreamweaver.
CodeBurner: It is an extension of Firebug reference tool for web developers. It shown the syntax, code samples, and browser compatibility information.
HttpFox : Monitors all incoming and outgoing HTTP traffic.