Facebook, Twitter and YouTube are out, but in China's vast and bewildering online universe you can freely read the New York Times or visit a favourite porn site.
People outside China who have read about Internet censorship -- thrown into the spotlight by Google's decision on Monday to close its mainland Chinese-language portal -- often imagine online life there is bleak and boring.
The reality is very different.
China's 384 million Internet users, the world's biggest online population, enjoy everything from gaming and celebrity gossip to teenage chatrooms, academic forums and illegal file-sharing sites.
English language media reports, some highly critical of Beijing, are usually as freely available as the hardcore pornographic sites the government regularly professes to crack down on.
But Twitter, Facebook and many overseas blogging sites are out because they allow rapid sharing of information, triggering the ruling Communist Party's fears of mass unrest.
Another touchy point for government censors are contested history, politics and religion.
Sites with more than cursory or officially sanctioned information about topics including the bloody 1989 crackdown on protesters around Tiananmen Square, or the banned Falun Gong spiritual cult, are usually blocked in China.
Total outage is however the weapon of last resort for a sophisticated censorship apparatus that wants to damp down dissent, while allowing room for commercial development.
First stop is media and website editors, who have a good sense of what Beijing will and won't allow, and are regularly contacted by officials with more detailed instructions on sensitive issues.
Topics can be taken off the front page of a website, the comment function can be disabled on controversial stories, or orders given to only use official state reports on some news.
Beijing is also believed by some analysts to fund a vast "50 cent" army, who roam websites making government-approved comments, and receive a tiny commission for each one.
Yet the censors' vast reach and power are shrugged off by many in China searching for anything from a favourite video on YouTube to news about a corrupt official.
In hi-tech games of cat and mouse, they try to spread blog posts faster than censors take them down, and joke about "harmonized" or deleted messages, in a satirical reference to President Hu Jintao's vision of a "harmonious society".
And for those with the inclination and money, the whole network of shut-down sites can be conjured up again through paid virtual private networks (VPN) which essentially allow them to tunnel through the great firewall at will.Report Typo/Error
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