Inside AdSense: On your frequency

Inside AdSense: On your frequency:
In the coming months, we'll be rolling out some new foundational features in AdWords for the content network. These features are intended to enhance your earning potential and the effectiveness of ads we serve to users on your sites. Some of the benefits of these features include:

• Frequency capping, which prevents users from repeatedly seeing the same ads on your pages.
• Improved attribution, to help advertisers identify the best performing sites in the network based on post-impression activity.
• Improved ads quality, as we're able to improve ad performance within the Google content network.

You can read about these in more detail on our official Google blog. To enable these features, we'll be implementing a DoubleClick ad serving cookie on the content network. We now have a program policy that covers data usage related to the launch of these new features.More from source