There are a number of standards/guides on how to cite materials found on WWW, discussion lists, databases, etc. These include:
(a) ISO standard DIS 690-2: very detailed international standard. http://www.nlc-bnc.ca/iso/tc46sc9/standard/690-2e.htm
(b) MLA style citation: practical guide to citation produced by Janice Walker. http://www.cas.usf.edu/english/walker/mla.html
(c) IFLA has a WWW directory of such guides: http://www.ifla.org/I/training/citation/citing.htm