Microsoft Internet Explorer has it and so does Firefox. Now Google Chrome will (reluctantly) have it too. The do-not-track option lets the user opt out of allowing their online activity to be tracked. Google decided to add the option as part of an agreement with the United States government. The option will appear in the Canary build of Chromium and could appear in the general release of Chrome by the end of the year. Both Firefox and Microsoft Internet Explorer already provide the option for their users. Microsoft, who has been particularly aggressive in implementing the option, has made it the default setting in Internet Explorer 10.
Since the do-not-track option requires webmasters to opt-in and activate do-not-track processing on their servers, experts feel inclusion of the option in the browser is a moot point since bad actors are not going to set it up on their web servers anyway.