HttpFox
HttpFox monitors and analyzes all incoming and outgoing HTTP traffic between the browser and the web servers.
Clear Cache Button
Adds a clear cache toolbar button. After installing the extension, find the clear cache button in the toolbar customization panel.
MeasureIt
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Web Developer
The Web Developer extension adds a menu and a toolbar with various web developer tools.
Cache Status
This add-on adds a customizable presence to your browser window's statusbar that gives you
up-to-date information on your browser's cache usage, both RAM and the hard drive.
Firebug
Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse.
You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.
Firecookie
Firecookie is an extension for Firebug that makes possible to view and manage cookies in your browser.
Locationbar
Puts emphasis on the domain to reduce spoofing risk, linkifies URL segments.
uToolBar
Toolbar for uCoz users.
Ctrl-tab
Ctrl+Tab navigation and "All Tabs" panel
Session manager
Session Manager saves and restores the state of all windows - either when you want it or automatically at startup and after crashes.
It can also automatically save the state of open windows individually.
CoLT
CoLT makes it easy to copy either a hyperlink's text or both the link and the link's text (in a format you specify). Two handy context-menu items make this possible,
and don't add clutter; the items are only visible when right-clicking a link!
Popup ALT Attributes
Popups alternate texts of images or others like NetscapeCommunicator(Navigator) 4.x, and show long descriptions in the multi-row tooltip like MSIE.
Save image in Folder
Easily save images in personally customized folders.
QuickDrag
Extends the function of the drag-and-drop mouse gesture so that it can be used to load URLs, do a web search of selected text on a page,
or save an image on a page.
Cookie Monster
Cookie Monster provides proactive cookie management on a site or domain level basis, including 3rd party cookies. Via the status bar,
it provides easy access to enhanced cookie functionality, while doing so in a non-intrusive manner.
Extended Status bar
A Statusbar with speed, percentage, time and loaded size (similar to Opera's one)
Menu Editor
Customize application menus: Rearrange or remove menuitems from the main context menu (right-click menu) and main menubar (File Edit View etc.)
Personas Plus
Free, easy-to-install "skins" for Firefox. Choose from over 180,000 cool designs, including art from Harry Potter and Bob Marley.
Join over 8 million people from around the world who are asking themselves: "What Will My Browser Wear Today?"
Google Docs Viewer
View PDF, DOC, DOCX, PPT, PPTX and TIFF files online with Google Docs, i.e. a right-click on a link and another for "Open". Supports bookmarked URLs.