The Best of Yahoo on Firefox, get Extension pops up every time I start Firefox. How can I get rid of this?
If I select "cancel", it still comes up next time I open Firefox. Blocking Pop-ups doesn't help, either.
It is possible that there is a problem with the file(s) that store the extensions registry.
Delete the extensions.* files (e.g. extensions.json, extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry.
New files will be created when required.
See "Corrupt extension files":
If you see disabled or not compatible extensions in "Firefox/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.
If this hasn't helped then also delete possible addons.json and addons.sqlite files.
You can also check for problems with preferences.