Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
The easy way to download and convert Web videos from hundreds of YouTube-like sites.
This works also for audio and picture galleries.
The first and only download manager/accelerator built inside Firefox!
Find out which websites you can trust. WOT adds intuitive traffic light-style icons next to search results and URLs to help you make informed decisions about whether to visit a site or not.
LastPass, an award-winning password manager, saves your passwords and gives you secure access from every computer and mobile device.
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Lightbeam is a Firefox add-on that enables you to see the first and third party sites you interact with on the Web. Using interactive visualizations, Lightbeam shows you the relationships between these third parties and the sites you visit.
View HTTP headers of a page and while browsing.
Just another speed dial extension. Fast and easy to use.
Proxy Selector lets you switch local proxies in Firefox.
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)
Control what gets sent as the HTTP Referer on a per-site basis.
Manages the Remote XUL whitelist to allow websites and local files to load XUL content.