Windows 7: Online tool reveals 'fingerprint' browsers leave.

The Electronic Frontier Foundation has created an on-line tool that details the wealth of information a Web browser reveals, which can pose privacy concerns when used to profile users.

The EFF's Panopticlick tool takes just a few seconds to pluck out information that a Web browser divulges when visiting a Web site, such as a user's operating system, version numbers for plug-ins, system fonts and even screen size, color and depth.

Taken together, that information is a unique fingerprint for a particular PC, which could be used to repeatedly identify a particular visitor a Web site, the EFF said.