Privacy Badger is a browser add-on that stops advertisers and other third-party trackers from secretly tracking where you go and what pages you look at on the web. It is available for the Firefox and Chrome browsers (and there are plans to make versions for Opera and Firefox Mobile).
I recommend this add-on instead of the Disconnect or Ghostery add-ons. Privacy Badger is better overall, because it just works “out of the box” — without requiring a user to perform custom configurations. Also, Privacy Badger was created by the Electronic Frontier Foundation, and hence it is not linked to any corporate agenda.