What is the DoubleClick cookie doing on my computer?
If you have a DoubleClick cookie in your Cookies folder, it is most likely a DART cookie. The DoubleClick DART cookie helps marketers learn how well their Internet advertising campaigns or paid search listings perform. Many marketers and Internet websites use DoubleClick’s DART technology to deliver and serve their advertisements or manage their paid search listings. DoubleClick’s DART products set or recognize a unique, persistent cookie when an ad is displayed or a paid listing is selected. The information that the DART cookie helps to give marketers includes the number of unique users their advertisements were displayed to, how many users clicked on their Internet ads or paid listings, and which ads or paid listings they clicked on.
Why does your cookie keep coming back after I delete it?
When you visit any website or search engine on which DoubleClick’s DART technology is used, our servers will check to see if you already have a DART cookie. If the servers do not receive a DART cookie, the servers will try to set a cookie in response to your browser’s “request” to view that Web page. If you do not want a DART cookie with a unique value, you can obtain a DoubleClick DART “opt out” cookie. Alternatively, you can adjust your Internet browser’s settings for handling cookies. This is explained in the next question.
How can I adjust my cookie settings to accept or decline cookies?
To eliminate cookies you may have currently accepted, and to deny or limit cookies in the future, please follow one of these procedures:
IMPORTANT: IF YOU DELETE YOUR OPT-OUT COOKIE, YOU WILL NEED TO OPT-OUT AGAIN. IF YOUR BROWSER BLOCKS ALL OR THIRD-PARTY COOKIES, YOU WILL BLOCK THE SETTING OF OPT-OUT COOKIES.
This article from Norton Security describes how to manage cookies on a variety of devices and browsers.