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).
Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
2,723 weekly downloads
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Note from Mozilla: This add-on has been discontinued. Try Updated Ad Blocker instead.
It blocks ads on the web pages you visit.
British English Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey by David Bartlett.
To enable, right-click in a multi-line text box, select "Languages", then "English / United Kingdom".