While you can combine this with Adblock Plus for better ad blocking, it is an understatement to say that this is annoying:

Sometimes when you hide an element, the hidden element appears, especially on the first page you load after starting Firefox. It even happens if you have both uBlock and ABP installed with the filter on both of their lists.

This is why I gave it four stars. I would have given it five if this weren't an issue.

This happens on Google Chrome as well.