If you are a web developer you need to use different tools to check various aspects of the pages and websites. Be it HTML validation or page alignments or performance of the pages, you need to carefully test the page and optimize it to become production ready website. In this scenario the browser based add-ons that does most of these activities will help you to a great extent.
Firefox browser with the support from hundreds of plugins developers across the globe has released some of the best tools to help you in developing and testing your web pages and web sites. Here is my list of  good Firefox extensions and plugins that will help you make web development activities bit more easily.
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Best Firefox Web Developer extensions

Web Developer

The Web Developer Firefox extension adds many useful web developer tools to the Firefox browser. For example it adds options to manage cookies, CSS, Images, page objects like JavaScript’s etc. The tool provides options to validate CSS, Links, DOM inspector etc. The page resize tool, outline options, rulers, expose hidden fields etc are really useful features.
This is a very useful extension for web developers.
Try Web Developer

Firebug

Firebug is a complete web page analysis tool. We have discussed about Firebug in one of our earlier post. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page using Firebug.firebug-large
Try Firebug

YSlow

YSlow analyzes web pages and why they’re slow based on Yahoo!’s rules for high performance web sites.YSlow is a Firefox add-on integrated with the Firebug web development tool.
Try YSlow

ColorZilla

ColorZilla provides tools like Eyedropper, ColorPicker, Gradient Generator right from your browser. You dont have to open software like photoshop to find out the pixel color in the browser. It is easy using ColorZilla.The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes.colorzilla
Try ColorZilla

MeasureIt

MeasureIt draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels. This is again a useful Firefox extension for web developers.
Try MeasureIt

User Agent Switcher

User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
Try User Agent Switcher

Html Validator

Html Validator adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon.
Try User Agent Switcher

View Source Chart

View Source Chart Firefox add-on helps us to inspect the DOM. The extension places visual boundaries to the source code.
Try View Source Chart

Binu GeorgeBrowser Tipsfirefox developer extension,firefox developer plugin,Firefox extension,how-to guides,productivity,web developer extension,web developer plugin,web developer toolbarIf you are a web developer you need to use different tools to check various aspects of the pages and websites. Be it HTML validation or page alignments or performance of the pages, you need to carefully test the page and optimize it to become production ready website. In...Tech-Knowledge that helps