A couple of people have told me that my site has been rejected by various content filters because it's believed to be a porn site.

My site is a humor site, and everything on it is safe for work. On one or two occasions I have linked to something that might not be work safe, and warned people of this fact next to the link. But the site itself is clean.

Who maintains these databases of unsuitable sites, and how can I get taken off of them?