Prof. Froomkin (welcome back!) links to a tracking cookie opt-out page:
With a few clicks you can block cookies from Doubleclick and six other Internet tracking/marketers. Ironically, you must allow the site to set a “no thanks” cookie, so cookie blockers must be turned off to make this work.
Although this site was a good idea once upon a time, this rigmarole is completely unnecessary. Tracking cookies are, by definition, third-party cookies. I can think of no good reason to allow third-party cookies on my computer, and so I block all of them. You’ll find the detailed instructions in this article I published in January of this year: How to completely eliminate tracking cookies.
The article includes instructions for Internet Explorer and Firefox. I just checked my system, and despite the fact that I have not deleted any cookies in the past year I have no tracking cookies from DoubleClick, Atlas DMT, 24/7 Real Media or any of the other sites listed on this page.