Do Not Track is a common term to describe a way for people to opt out of online behavioral advertising. Yahoo's Do Not Track tool has been in development since last year and is almost ready for prime time.

Yahoo said its tool is in accordance with the Digital Advertising Alliance's principles. This sitewide Do Not Track mechanism -- which also includes Yahoo-owned Right Media and Interclick -- promises to provide a simple step for consumers to express their ad targeting preferences on Yahoo sites.

"Yahoo has decided, for PR reasons, to get out in front of Do Not Track and be seen as responsive to consumers and their privacy concerns rather than dragging their feet," said Greg Sterling, principal analyst at Sterling Market Intelligence. "Everyone eventually will need to do some version of this. Yahoo is wise to seize the initiative and gain the positive exposure that will come with it."

Mozilla's Do Not Track Version

Mozilla plans to offer a feature to let users opt out of online behavioral advertising. Dubbed Do Not Track, it's the Firefox maker's latest effort to put users in control of their Web experience.

Mozilla is proposing a feature that allows Firefox browser users to set a preference that will broadcast their desire to opt out of third-party, advertising-based tracking by transmitting a Do Not Track HTTP header with every click or page view in Firefox.

"When the feature is enabled and users turn it on, Web sites will be told by Firefox that a user would like to opt out" of online behavioral advertising, said Alex Fowler, Mozilla's head of privacy. "We believe the header-based approach has the potential to be better for the Web in the long run because it is a clearer and more universal opt-out mechanism than cookies or blacklists."

Google's Chrome Efforts

Google also offers a feature that lets Chrome browser users opt out permanently from ad-tracking cookies. Dubbed Keep My Opt-Outs, the extension is available as a download.

Google developed the feature for the same reason as Mozilla: The Federal Trade Commission, among others, has expressed interest in a Do Not Track mechanism offering users a simple way to opt out of behavior-based advertising.

Opting out of personalized ads is nothing new. Technologies exist that even let customers tailor personalized ads by specifying what types of ads they are most interested in. But Google and Mozilla both pointed to technical challenges with these opt-outs and controls.