Really great article from CNN about China censorship.

"Every Chinese person who signs up for Internet service must register with his or her local police department within 30 days.

Blogs, discussion forums, and bulletin boards are very popular in China. They're heavily filtered by keyword blocks. Blogs' service providers do not let posts with certain words be published, and blogs are also censored manually.

Here's a short list of keywords that will trigger the filtering system and block access to content:
# Revolution
# Equality
# Freedom
# Justice
# Taiwan
# Tibet
# Falun Gong
# Dissident
# Democracy
# STD
# Human rights "

http://www.cnn.com/interactive/world/0603/explainer.china.internet/frameset.exclude.html