The Web Developer extension adds various web developer tools to the browser.
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...
Color tools for web development.
Color picker and eyedropper + saving colors and trying out colors with drag and drop.
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon
For Firefox 23+, you need 0.958 (under review)
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
Collections are groups of related add-ons that anyone can create and share.Explore Collections