I am an Adsense Publisher for several years. Usually I carefully try to use the new features.
Most probably in last year, adsense introduced adsense optimization report. Each month, it shows an report of previous month. If its May, 2008 they will show April 2008 Optimization Report. After clicking on the link, I got two maximum reports. One Placing more than one ad unit on a page often generates more revenue.
Many of your sites only contain one ad unit.
and second You may be filtering ads that monetize well on your site.
I did not see any other message in my life with adsense. However, none of the messages came to any use for me. I think, both the messages, specially the first one is too much gross. It says, placing more than one ad unit on a page often generates more revenue. But it doesn’t show any indication where only one ad unit is displaying. I show ads on more than 10 domains and in several hundreds pages. Ads format on each website is different. Even varies from page to page of same website. So, its not easy for someone to check where there is only one ad unit is displaying. But adsense can tell it very easily. If it can’t, I don’t see any use of it.
Most probably, you must see the second one if you filter any ad(s). So far I remember, I have filtered only one domain. After that, I am getting this message. Unfortunately, that ads did not stop showing in my sites. I don’t know why. I have studied google adsense docs very well to filter ads. But it did not work for me. You may say, then why I did not report it to Adsense team. Its because I don’t like to hear rubbish robotic answers. Most of the times, I got the answer like ‘Adsense is a very young program…..your feedback is very helpful…..”. So, I don’t send any feature request and/or suggestion to them.
Anyway, I wish the adsense team will provide some concrete optimization tips intelligently based on the publisher ads publication.