This is among the best-of-the-best add-ons for Firefox. After extensive use of Adblock Plus, the internet has become practically unbearable using any other browser or configuration. Best of all, I can selectively turn it on and off across various domains. This allows me to activate ads on certain webpages, who I wish to support with ad-revenue, while neutering obnoxious ads on all other sites. Filter updates are very good, and it's easy to add your own. I highly recommend Adblock Plus to any Firefox user, and always install it on every system I maintain.