Google ads on our site--more McCain ads

I'm always a little bit curious about the banner ads from google that appear on our site. An ad for John McCain appeared again on the very bottom of our main page. This is the second time I've seen a McCain ad on our site. In fact, his ads are the only political ads I've seen on our site. Not really genealogy news, but I wonder what demographics about my site visitors or text on my pages made them think it was worth placing the ad. Back to genealogy work...I'll keep looking for the dead..whether they were voters or not!