Due to the emergence and popularity of web blogs/forums and user orientated websites defamation over the internet has become an increasingly common concern.
Due to this, case law and judicial rulings have had to move with the times. Most notably the case of Laurence Godfrey v Demon Internet Limited  4 All ER 342 which ruled on the liability of the Internet Service Provider over comments posted on one of its websites.
In summary, if the ISP has been notified of a defamatory posting it is under an obligation to remove the same.
If the ISP does not do this then it becomes secondary liable for defamation.
In view of this ISP’s will often remove the postings do avoid an further action being taken and so this would be a good first step if you find something defamatory about you on a website.