And then there was Chrome.

Apple made it clear this week that the next version of its Safari browser — which will ship with the upcoming version of Mac OS — will include the ability for users to tell websites not to track them, by using what’s known as the ‘Do Not Track’ header, according to The Wall Street Journal.

It’s a technically simple change that Mozilla (the maker of Firefox) and Microsoft (the maker of IE) have already included in their newest browsers. Those companies included the change despite the fact that no one has actually defined what tracking is. So far only two ad networks, B...