The best and the most useful plugin for web developers and front-end engineers till date. It is a helpful and handy tool to analyze a web page markups, requests, responses, CSS and JavaScript performances. There is a inbuilt profiler which can give a comprehensive report of javascript method calls and time taken to execute each method in the browser window. The “Inspect” feature specially helps to inspect any element in the DOM tree of a web page. You can even extend your web page with special javascript calls to use “Firebug” as a logger for your javascript development. I use this plugin extensibly everyday.

The Web Developer extension adds a menu and a toolbar with various web developer tools. You have the option to disable all images, css and javascript. With this toolbar you can mark different elements in the mark up, measure width and height with an inbuilt ruler, resize the browser to a given resolution and do lot many things. A must have for the web developer and front-end engineers.

With ColorZilla you can get a color reading from any point in your browser, quickly adjust this color and paste it into another program. You can Zoom the page you are viewing and measure distances between any two points on the page. The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes. DOM spying features allow getting various information about DOM elements quickly and easily. And there’s more…

A simple CSS property viewer. Very simple but very handy tool for analyzing styles used for a particular element in a web page.

YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. YSlow is a Firefox add-on integrated with the Firebug web development tool. YSlow grades web page based on one of three predefined ruleset or a user-defined ruleset. It offers suggestions for improving the page’s performance, summarizes the page’s components, displays statistics about the page, and provides tools for performance analysis, including Smush.it™ and JSLint.

Page Speed is an open-source Firefox/Firebug Add-on. Webmasters and web developers can use Page Speed to evaluate the performance of their web pages and to get suggestions on how to improve them. Page Speed performs several tests on a site’s web server configuration and front-end code. These tests are based on a set of best practices known to enhance web page performance. Webmasters who run Page Speed on their pages get a set of scores for each page, as well as helpful suggestions on how to improve its performance.

It 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.

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. By toggling the composition on and off, the developer can visually see how many pixels they are off in development.

Selenium IDE is an integrated development environment for Selenium tests. It is implemented as a Firefox extension, and allows you to record, edit, and debug tests. Selenium IDE includes the entire Selenium Core, allowing you to easily and quickly record and play back tests in the actual environment that they will run.

Link Evaluator works as an enhanced Link Checker – both for the links on the current Web page and for the Bookmarked links.Link Evaluator examines both the HTTP status code and the page contents returned by each URL, and attempts to distinguish between various results, such as:

• broken links
• network time-outs
• authentication failure
• ‘incorrect/correct’ content for the given URL