It is simple to block unwanted ads on Firefox throughout the web. First open Firefox from Finder then to the Applications folder then to Firefox. Next copy this link into the address bar in Firefox https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/?src=cb-dl-mostpopular then click add to Firefox. You won't need to restart Firefox for the add on to work. Go to a site that typically has adds like Yahoo Answers or Quizlet you will now notice that the ads have been blocked. You will never have to deal with another irritating add again on the internet it also will block ads on You Tube. Refer to the video below for further instructions.