google_ad_placement.html © November 2007 Anthony Lawrence All Rights Reserved
Google recently introduced Placement Targetting. Simply put, this lets you create and fully describe ad channels that can let potential advertisers know what kind of content specific pages are providing.
For example, let's say an advertiser of a Mac OS X product would like to advertise here, but doeesn't want to waste impressions on any pages that aren't talking about Mac OS X. That's become much more important as Google allows advertisers to place CPM ads now. As they pay for every impression (every eyball that sees the ad) rather than per click, they definitely don't want those ads running on pages with little chance of being read by Mac OS X users.
Before channel targeted ad placements, there was no way to do that. But now, that advertiser can see that my "Mac" channel is described as:
This is the 300 x 250 rectangle that appears above the fold after the second paragraph of text. It only runs on pages related to Mac OS X.
Of course I have other channels defined for Linux, General Unix, Security and so on. These allow advertisers to target pages strongly related to the products they are pitching.
Previously, Google only allowed "site targeting" - an advertiser could run CPM ads on a specific website, but only site wide. Needless to say, that wasn't very popular with advertisers. There may have been some good matches; for example a sports equipment advertiser might have had good luck on any sports oriented site, but this now allows much more specific targets and should be more popular, at least with larger websites. Most smaller sites probably wouldn't benefit from this, though I don't see any harm in trying: approximately 10% of this site's Google revenue comes from site targeted advertising.
From the website side, this is a fair amount of work to set up. I use code that sets channels based on the tags I have placed on the articles; if you are not using script driven advertising, modifying a large website to take advantage of this new ability would be very difficult.