Thanks for the advice guys. I have been using AdBlock Plus for years - it’s a fantastic add-on and I never see ads on YouTube (or virtually anywhere for that matter). I used Chrome for a while but there were a few things that bugged me and I ended up back on Firefox. I think I am just going to make an account; I guess I can just delete it if things become even more annoying, but I doubt that’s possible.

AdBlock Plus Element Hider is great too, you can use it to block signature images, animated gifs and bunny skyscrapers. On the same topic of blocking unwanted/harmful crap, you can use your hosts file in Windows to block websites and popups that persist despite your browser settings: Blocking Unwanted Connections with a Hosts File The page makes it look fiddly but it is just a matter of finding the location, backing up the original and replacing it with the hosts file provided. You can also add to it yourself using Notepad.