Google Adsense

Of course, results will differ for different sites. Generally,
wrapping blocks of AdSense ads in between blocks of quality
content works well or placing them toward the top of the
page works well and boosts CTR. Another suggestion is if
you have links provided on the page, try placing your
AdSense ads on top of them. Since attention is
automatically drawn to links, having your ads above links
will help to increase your CTR.
Example: In this screen shot from
http://si-computers.blogspot.com, notice how the ads are
wrapped in with the text. A visitor can’t help but notice the
ads. Also, note that the ads are directly targeted toward the
text. The ads offer resources for downloads and services
related to the world of technology that is spoken about in
the text. This wasn’t done on accident. The Webmaster has
optimized the site, using keywords and text targeted toward
visitors. Therefore, the AdSense ads easily blend in, not
only to the design, but the information on the page as well.
This site is an excellent example of successful SEO and
AdSense knowledge.