Adsense wanted to let you know about two recent changes to their site targeting feature. As you may know, site targeting allows advertisers to select specific publisher sites on which to run their ads. Advertisers can target your site if they've determined a match between their offerings and the interests of visitors to your site.
The first change is that we’ve renamed 'site targeting' to 'placement targeting' to better reflect the variety of targeting options we offer. Advertisers can still target their ads to an entire site, but they can now also target your individual ad units or groups of pages based on how you’ve set up ad placements using custom channels. Over the next few weeks, we'll be updating references to 'site targeting' in your account and in our Help Center.
The second change is that advertisers can bid on placement-targeted ads (formerly known as site-targeted ads) on a cost-per-click (CPC) basis. Previously, advertisers could only bid on these targeted ads on a cost-per-impression (CPM) basis. Just as with contextually targeted CPC ads, you’ll generate earnings for valid clicks on placement-targeted CPC ads.
While you can also add the URLs of specific CPC placement-targeted ads to your filter list, please keep in mind that all placement-targeted ads will participate in the ad auction with contextually targeted ads. Allowing more ads into the auction will help increase competition and ultimately your revenue.
Finally, we'd like to leave you with a few reminders to help you maximize your revenue potential with placement targeting:
Turn your custom channels into ad placements. These ad placements will allow you to highlight specific sections of your site that may appeal to advertisers.
Enable text and image ads for your ad units. By opting in to different ad types on your site, you'll increase the competition in the ad auction, which can lead to additional revenue for your account over time.
Use the 300x250 Medium Rectangle. This ad format is one of our best-performing ad units, and many advertisers use it when creating rich media (image and video) campaigns. Again, you'll benefit from the increased competition for your ad space.
For more: Adsense Blog