Via the Adsense blog:
If you’ve been roving around the AdSense Help Center, you may have noticed there’s now a bigger, better version of our Optimization Tips page. If you’re new to optimization, or just looking for some new ideas to increase your earnings, you may find the new page especially helpful. We’ve added more info on choosing successful color palettes and how to enrich your site through effective use of Google services like Blogger, AdWords, and Sitemaps (among others). You’ll also find new, detailed suggestions for improving your AdSense performance on specific kinds of sites like blogs and forums. Many of the entries now include images like screenshots and heatmaps to make our tips easier to understand, and we think the new layout will make the whole thing easier to absorb and implement.
With each passing day, I see Adsense encouraging webmasters to optimize their ads and websites, and YPN telling webmasters you can’t use images, do this, you can do that.
One must wonder why Adsense gets a higher fraud rate. Go figure.