The_Shower_Scene - 7:48 am on Jul 25, 2011 (gmt 0)
999,999 out of a million, it's better if YOU tell us a little more about your site so that we can then tell you what's going on. Usually it's crap content and/or promotion. But not all the time.
No offense intended, but most people who post these kinds of posts are in a scary level of denial. I'm not saying you are, but that's where all the OTHERS are.
If you want more specific advice, then you will have to provide more specific details about how you promoted your site and how the content came about. Other than that, I and we can only assume. So give us more details and you will receive a more specific response.