Firefox extension that replaces the JavaScript Console. Display errors filtered by type (Errors, Warnings, Messages), language (JavaScript, CSS, XML) and context (Chrome, Content). Useful for web and extension developers.

Allows the user to add, modify and filter out HTTP request headers.

Extensions for HTML, CSS and RSS validation.

cuneAform has been designed to create a HTML Editor that anyone can use.

Toolbar extension for helping penetration-testers test the security of websites, networks and webpages.

A list of extensions built primarily for web designers and programmers.

Adds a JS Console context-menu item which presents a "Toolbars" submenu for hiding or showing the eval / mode toolbars.

Shows all the output generated by any running flash swf movies ( the output generated by the trace flash method ).

Facilitates the making of add-ons with standard web technologies so that anyone who can make a website can make an add-on.

A tool that can be used to inspect and edit the live DOM of a web document or XUL application. Restores functionality present prior to Firefox 3.0. Description and user comments.