According to Byron Acohido from USA Today, Facebook has been able to create a running log of visits that each of its 800 million members has visited in the previous 90 days. Once you are logged into Facebook, the site inserts a both a browser cookie and a session cookie into your web browser.
“Online tracking involves technologies that tech companies and ad networks have used for more than a decade to help advertisers deliver more relevant ads to each viewer. Until now, Facebook, which makes most of its profits from advertising, has been ambiguous in public statements about the extent to which it collects tracking data.”
In a nutshell: If you are logged into your Facebook account and also surfing the web, it is your session cookie that will log any third-party web pages that you visit. This session cookie works in conjunction with any Facebook plug-in (such as the “Like” button) that is installed at the third-party site and reports back to the FACEBOOKSHIP: the web address of the page you visited along with pc and browser data including your IP address.
To get out the full scoop on how Facebook tracks you across the web, be sure to visit USA Today and view their flash presentation on how this process works once you are logged in, logged out and how Facebook currently uses this tracking technology.