<i>Search engine optimization affects only organic search results, not paid or "sponsored" results such as Google AdWords.</i><p>That's not entirely true. On-page SEO can affect AdWords Quality Score, which in turn can affect position in "sponsored" results lists ("The quality of your landing page" - <a href="http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=10215" rel="nofollow">http://adwords.google.com/support/aw/bin/answer.py?hl=en&...</a>)