A style manual by Janice R. Walker and Todd Taylor, published by Columbia University Press. It is based on Walker's earlier Walker/ACW Style Sheet. It covers both production of documents and citation of other documents online.
CGOS describes a standard style for citing a wide variety of online sources: documents found via the World Wide Web, Gopher, FTP, and Telnet; email, mailing lists, and newsgroups; "synchronous communication sites," such as chat rooms and MUDs; reference works located online; electronic publications and online databases; and software titles, including video games.
For example, here are citations of the pages used as references for this writeup:
Columbia University Press. "About the Columbia Guide to Online Style." 20 Mar. 2000. http://www.columbia.edu/cu/cup/cgos/index.html (11 Mar. 2001).
Columbia University Press. "Basic CGOS Style." 20 Mar. 2000. http://www.columbia.edu/cu/cup/cgos/idx_basic.html (11 Mar. 2001).