Legal Question in Intellectual Property in California

Choosing an appropriate course of action may depend upon, in addition to the factors you mention ("very negative, false"), (a) the likely number of others who have looked at the website and seen the information, (b) whether you can establish and prove any financial consequences, and (c) whether the "information" is defamatory "per se". For a definition of per se defamation, your best bet is to look it up on Wikipedia or other on-line sources. If warranted, threatening or actually bringing a lawsuit is a possibility.

Here is another Web site that may be helpful in understanding what slander, libel and defamation amount to, and in understanding some special problems in bringing legal actions against Web site operators and users who may be in far-away jurisdictions with different laws and can be hard to bring suit against:

https://www.eff.org/issues/bloggers/legal/liability/defamation

A letter from an attorneys office may be helpful. if you would like a free initial consult, call me at 8187837998