This BBC article looks at the many and varied ways China controls the surfing of its citizens.
An excerpt:
Part of the net's allure to Western users is the sense of freedom it gives them to look at, read, and say almost anything they want.
By contrast, Chinese net use is much more circumscribed.
Much has been made of the so-called Great Firewall of China that censors what people see using technology built in to the country's basic net infrastructure.
The Chinese authorities have used several methods to "sanitise" what people see online, according to a report from US firm Dynamic Internet Technologies, which watches net use in the country.
On the most basic level, the firewall blocks net addresses hosting webpages that the authorities would rather people did not see. Anyone trying to visit these pages gets told that the page cannot be found or does not exist.
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 Surveillance is much easier in cyberspace than in the real world  Julien Pain, Reporters Without Borders |
Also China has changed its core net address books, known as Domain Name Servers, which tell a user's computer where to find a particular webpage on the net.
The sites blocked by these techniques include the many dealing with taboo subjects such as Tibet and Falun Gong as well as the BBC News website, search engine Google, sex sites such as Playboy and many blogs.