From Xinhua News Agency (link):
A dozen of major Beijing-based Internet portals have called for the industry’s joint efforts to clean their Websites off unhealthy contents, especially messages of sex and violence.
In a joint proposal drawn up on Sunday, owners of 14 websites, including Sina.com, Sohu.com, Baidu.com, and Yahoo’s Chinese Website, called on all Internet portals across the country to stem “unhealthy Internet cultures.”
Also see Xinhua’s special report on Internet (link)
Also Wikipedia’s “Internet in China” and “Internet censorship in China”