I went to the Adblock Plus site and tried downloading/installing it again and this time, Firefox refused, saying the file appeared 'corrupt' so it would not install it. (For the record, I got the same error message for the Trend Micro toolbar, that it was no longer 'verified' so had been removed, though I didn't have it enabled.) Adblock Plus is literally the only addon I use. Just a bunch of Firefox addons I'm not interested in. It had a link to take me to other addons to replace the missing one but there apparently are none. Looking into the settings for further info, it said stuff about it no longer being verified in Firefox and took me to some page that described the issue but it didn't explain much, just something about 'improving' or updating itself to be safer removing my ad blocker sure doesn't make it safer. But a few moments ago when just sitting idle on Wikipedia, I got a popup from Firefox saying the addon isn't recognized anymore and has been removed. Have been noticing problems with Adblock Plus taking a while to start working when I start up Firefox lately.