The DoubleClick DART Cookie?
The DoubleClick DART cookie is used by Google in the ads served on publisher websites displaying AdSense for content ads. When users visit an AdSense publisher's website and either view or click on an ad, a cookie may be dropped on that end user's browser. The data gathered from these cookies will be used to help AdSense publishers better serve and manage the ads on their site(s) and across the web.
We may update this policy from time to time. We will notify you about significant changes in the way we treat personal information by placing a prominent notice on our site.