Received this message today from Google AdSense.
We performed an analysis on xyz.com and found a great opportunity to increase your AdSense earnings. We recommend that you change your 120x600 ad units to 160x600's on xyz.com. Here is an example of where we found this opportunity: xyz.com/
Generating the code for this new ad size should take no more than five minutes, and may have a substantial impact on your revenue. On average, publishers across our network who implement this change see a noticeable improvement on the CPMs and we think you’ll see similar results.
For an example of how small changes can make a big impact on your revenue, check out how CareerPlanner.com increased their revenue by 165% by making changes similar to the one I’ve suggested.
You'll get the best results by updating all 120x600 units across your site. Our system analyzed 1pages across xyz.com and found 3 120x600 ad units.
I know this is probably in their best self interest, but it also makes me money in the same way. So it’s a win/win in my book.