I believe rohit89 means something else. Imagine you visit IMDB, which contains resources from doubleclick.net that set a doubleclick.net cookie. Next, surf to t

I believe rohit89 means something else. Imagine you visit IMDB, which contains resources from doubleclick.net that set a doubleclick.net cookie. Next, surf to the WSJ which also has doubelclick.net content. Your browser could simply not send the doubleclick cookie because it knows that it came through IMDB and not through the WSJ. In order to do this, a browser (or extension) would need to track through which sites a 3rd party cookie was set, and only send the 3rd party if you're on that same site again. Else it should just pretend there is no 3rd party cookie. I'd definitely install an extension that would implement this process.