This is more of a minor annoyance than a serious issue. I see in dblog that I am getting this a few times a day - unfortunately it seems to be most often with the CEO.

 

I am getting a"Page not found" on URLs like http://www.example.com/valid_category/-//W3C//DTD%20XHTML%201.0%20Strict//EN. Obviously someone is picking up some of the DOCTYPE information.

 

Has anyone else ever seen this? Does anyone have an idea how to get it fixed?