What can I do??

[Ash2005]

Please tell me what I can legally do in this situation?. It may seem not a very big issue to others, but it is to me. Over the past 3 years I have been going to an internet forum, I really like it and I have made many friendships there. 6 months ago a man joins up and starts picking on me, no one else, but he seems to have something against me, Why?, I don't know why, I have done NOTHING to make him do this to me. He slanders my name everywhere, not just on that forum, as he is banned from there now, but other forums of his. He says really vulgar things just horrible, He has gone as far to state he wished I was dead and awful things about my family, its stressfull and upsetting and I want it to STOP. Please what can I do?. I'm under the impression I can do nothing, but if theres anything I can do, I will do it!.