Danny Yee >> Internet Censorship in AustraliaAgainst Labelling (ICRA/RSACi)
The best known rating system for labelling Internet content is ICRA (which was RSACi). The details of this can be found (with effort) on ICRA's web site; Charlie Stross has written a more accessible description.
How anyone can support RSACi is beyond me. It has no provisions at all for scientific, literary, artistic, or political material. So a Rubens nude must be rated the same way as a Hustler centerfold, Alex Haley's Roots is indistinguishable from a soft-porn novel Nazi Masters Teen Slut, and pictures of concentration camp victims might as well be snuff movies as far as RSACi can tell. Nor can it distinguish films from text. But this scheme, according to RSAC, "empowers the public, especially parents, to make informed decisions about what they and their children experience on the Internet"!
Note: ICRA adds "appears in a context intended to be artistic/educational/medical and is suitable for young children" labels, but that doesn't help with artistic/educational/medical resources that aren't suitable for young children. And one parent's "sex education" is another's "pornography".
Response to an RSAC/Netscape PR (June 1998) A 1997 exchange
EFA Condemns RSACi | Irene Graham
the ABA Speaks | my response
RSAC SpeaksOther Sites
criticism of the Japanese ENC system
Rating Does Not Work
Richard Clayton
The Net Labelling Delusion (Irene Graham)