I have a site for funny pictures that are uploaded by users. The pictures are with funny animals & people... I know maybe some of them are copyright and i can't use them but i have written that users should not upload pics that they don't have the rights for them. My question is: can i put watermark on them? the logo of the site or something like "seen on ..." or "hosted on ...."? Thank you
All pictures have an automatic copyright - you need permission or release from the owner - i.e. if you take a picture, you are the copyright holder and people would need your permission to use it.
If you've written that users can only upload their own images, why don't you just put a little note saying "By uploading you agree that we can place a small watermark on your image". That's what I would do. It seems as if you are doing everything you reasonably can to prevent copyrighted images appearing on your site, so i wouldn't worry too much about that aspect, even though you're technically liable.