Over the past year there have been many capabilities added to web browsers to allow users to indicate their willingness to be tracked across various sites for web advertisements. While the implementation by individual hosts is optional, the user can sent the request to identify their personal preference. Tracking can be relevant to allow for more “targeted” ads tailored to each user.
Firefox 4.0 betas added an
"X-Do-Not-Track:1" HTTP Header. Later implemented Firefox 5.0 betas as
navigator.doNotTrack, with a value of “yes” when set.