What a Do Not Track option might look like

How would a Do Not Track registry work? Not quite like the popular Do Not Call list its name implies, experts say. The latter is a phone list that's off limits to telemarketers. The former would be a tool on Internet browsers designed to block third-party companies from collecting information on the Web sites a user visits.

"It employs a very different approach; the developing consensus is not around a list or registry," said Stanford University computer science researcher Jonathan Mayer. Rather than entering their names on a centrally maintained list, Internet users who don't want advertisers and other firms to follow them on the Web, would use technology to block tracking -- specifically, a tool on their Web browsers. DoNotTrack.us, a collaboration by Stanford Universities offers one idea for how such a tool would work: Whenever an Internet browser requests content or sends data using HTTP, the protocol that underlies the Web, it can optionally include extra information, called a "header." Do Not Track simply would add a header indicating that the user does not want to be tracked.