Adblock Plus

Adblock is a helpful extension that allows you to hide annoying images, iFrames, or Embeds. Most commonly this is used to block ads. However, you can also use it to get rid of other things - for example, if someone has a forum avatar you don't like, you can get rid of it on your machine so you don't have to look at it again. The Plus version is superior to the original because it also includes a function that lets you subscribe to a list of blocked ad servers, so that you will always stay ad-free.