Here are the OdoGoddess' Rating Rules
[G] contains absolutely no sex and no violence. Suitable for all ages.[PG] contains no sex, although sex may be implied. There may be mild violence (hitting, swearing).
[PG13] contains innuendo, stronger references to sex, but no actual depiction of sexual content. May contain violence and language inappropriate for children under 13.
[R] contains consensual sex and/or violence, and can contain strong language. Older teens are probably okay with it, younger teens might find action or dialogue disturbing or confusing.
[NC17] contains graphic depictions of sex and/or violence. May contain non-consensual sexual activity. Absolutely no readers under the age of 17!