The DNT draft specifications define three distinct states for the Do Not Track header
Mozilla was one of the Do Not Track pioneers and the first to implement it, in Firefox. While Do Not Track doesn't seem to be going anywhere as the technology is stuck in limbo thanks to all the "political" fighting, Mozilla is still working on the feature.In fact, the latest change to the way Firefox implements Do Not Track is a direct result of all the politics. Firefox will soon start offering more options for Do Not Track.
Currently, Firefox either doesn't tell websites anything about the user's Do Not Track (DNT) preference, because it hasn't been set, or it tells websites not to track the user if the option has been enabled.
The Do Not Track standard, still in draft form, defines three states, however, one when DNT is enabled and users don't want targeted ads and the likes, one when DNT is disabled if users are OK with being tracked and one when neither DNT state has been selected, if users haven't made up their minds.
These three states were defined shortly after Microsoft decided to make DNT the default in Internet Explorer 10, going against the wishes of both browser makers and the advertising industry. It's this move that has pretty much derailed any conversation around DNT.
These three states were created because there is a difference between a user who hasn't made any choice regarding DNT and a user that wants to be tracked. But Firefox is the first to actually implement the three different states in the settings and enable users to switch between them.
Firefox could have just added two options and, unless users picked either of them, don't send any DNT header accounting for the third state. But Mozilla wants to give users full control over the choices, as the browser maker generally does.