I have been using this blocker for years. I have never had any problems with it (bite me, YouTube!). Whenever I help family members or friends set up a new computer I always tell them to 1) install Firefox, 2)Install AdBlock, 3)never turn it off unless they absolutely trust the site.
This is the best ad blocker I have ever used and I have test driven several of the other blockers.

Best extension!

i'm completely satisfied..