To go along with my post on Essential OS X Software, here’s my list of “Essential Firefox Extensions”.
All-In-One Sidebar All-in-One Sidebar is a sidebar control, inspired by Opera’s. It lets you quickly switch between sidebars, view dialog windows such as downloads, extensions, and more in the sidebar, or view source or websites in the sidebar. It includes a slide-out button and a toolbar, all of which can be extensively customized.
All-In-One Sidebar provides enhancements for many built-in features
Colorzilla It assists web developers and graphic designers with color related tasks - both basic and advanced.
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.
Greasemonkey Greasemonkey is a Firefox extension which lets you to add bits of DHTML (“user scripts”) to any web page to change its behavior. In much the same way that user CSS lets you take control of a web page’s style, user scripts let you easily control any aspect of a web page’s design or interaction.
lori (Life-of-request info) This is a Firefox extension to add the following functionality to Firefox. * track how long it takes to see the first byte from remote server (time-to-first-byte (TTFB)). * track how long it takes to complete displaying the page (time-to-completion (TTC) * track the page size * track number of sub-requests used to build the page
MeasureIt Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Tab X Adds a close button to each of the browser tabs, and removes the close button at the end of the tab bar.
Tabbrowser Preferences This extension provides a comprehensive UI for changing a number of the hidden tabbed browsing preferences in Firefox. It also provides the ability to control how internal and external links are opened in the browser and how the browser will react when links are sent to it.
Web Developer The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools.