Public Service Ads - They are non-paying ads that run when google doesn't have an ad to show and you haven't set up an alternate.
If PSA ads occur on your website check: - if your website has been indexed by google yet - you might want to use section targeting (from the source: http://adsense.blogspot.com/2006/01/stay-on-target.html)
Ok thanks everyone, ive took all o that info in and im still waiting for my email back from google to see if my site has been accepted.