1script - 6:10 pm on Apr 29, 2010 (gmt 0)
Don't worry about it too much - it is showing SEO ads TO YOU because you've been to SEO-related sites (such as this one) and some ran AdSense. They got your cookie/IP and now know that you are interested in SEO - "interest targeting" I think is the term. Your actual visitors are seeing ads about other stuff that interests them - no less irrelevant to your site - if those ads promise to have a higher CPM than the ads related to the theme of your site.
Again, nothing to worry about - it's normal.