Any content that may be seen as an embarrassment to the government or is overtly anti-government won't be online for long. Chinese artist Ai Weiwei was jailed for three months in 2011 for speaking out against the government, and is currently barred from leaving China. Activist sites, news sites, and political pages are all under constant surveillance and are at risk for deletion. New keywords are blacklisted and filters are implemented whenever a new event occurs that could possibly show the government in a bad light.
Embarrassing the Government? That's a No-No