If you have watched the Matt Cutts video from WordCamp San Francisco 2009 you probably noticed his mentioning of the two following HTML codes
1.–google_ad_section_start–
2.–google_ad_section_end–
Most people don’t know about those two tags and so they don’t use them. Using them lets you define what part of your website (or blog) should be used to tell AdSense the kind of ads you want displayed.
For instance, I currently have a teaser on my TechPatio frontpage that mentions a really fast gunman and so my AdSense in the sidebar shows an ad for “gun safety”, even though that’s not really relevant for my tech blog. That was just an example, imagine if you did a post on how to perform better in the search engines and you would like
AdSense to show relevant banners, but because you have a good friend’s link in your blogroll about baby diapers,
AdSense might pick up on that and display an ad for diapers instead – thus you probably don’t get any clicks from webmasters on those ads.
Resource: Klaus www.TechPatio.com


