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When blogger Isaac Mao recently announced online an upcoming talk by a Beijing writer whose work is banned by the government, police showed up at his door at night to "convince" him to cancel the event. He agreed to, but just to be sure, authorities turned off the electricity of the planned meeting space and barred the doors.
Chinese officials say such actions are aimed at creating "social harmony." In the sarcastic lexicon of Chinese netizens, Mao was "harmonised" that April evening.
"They won't arrest you to stop you, but they pressure you," said Mao, whose website is blocked by the government. "They pressured the owners of this space and they threatened to close it down. Many people worry about losing their jobs. That's why many people self-censor themselves."
With more than 400 million Chinese now online - and another 100 million expected to join them by the end of the year - netizens are increasingly bumping against the limits of expression imposed by officials.
Google's recent decision to stop censoring its search site highlighted the tension between those who want an unfettered internet and government efforts to suppress "unhealthy" and "subversive" activity.
And it revealed to many Chinese how far the government will go to block certain information, Mao said.
China's leadership views the internet as an integral part of economic growth, but makes no apologies for censorship efforts so formidable they've been dubbed the Great Firewall of China.
President Hu Jintao has said the stability of the nation depends on the government's ability to "cope" with the internet.
The government is so determined to control public opinion that it hires bloggers - dubbed the "50-cent army" because of what they are paid per post - to promote its views online. It also backs censorship-friendly social networking sites.
And officials are considering a plan to require internet users to reveal their identity before commenting in public forums.
When "very allergic topics spread quickly" and the government can't block every internet posting about them, officials issue orders banning entire topics, pressuring companies that host discussion boards and blogs to fall in line, said tech blogger Hong Bo, who has received government warnings to stop writing on sensitive issues, such as Google's recent defiance of censorship regulations.
It's not uncommon for young people to alert friends through mobile phone text messages to blog posts they have written - and the importance of reading them quickly before they are blocked, said Lisa Li, founder of China Youthology, which examines the attitudes and beliefs of those 15 to 25.
"I think their strategy is to keep your criticism in a small circle," Liu Yan, who blogs, said of government officials. "They can't shut everybody's mouths."
The government, while promoting the internet as a tool for economic growth, wants "a safe internet in the sense that it is relatively controlled," said Guobin Yang, assistant professor at Barnard College in New York City and author of The Power of the Internet in China: Citizen Activism Online.
"But this is a contradiction. You can't have a controlled internet and still have it prosper. My guess is they don't have a very good strategy; they are just reacting to what is happening."
In the run-up last year to the 60th anniversary of Communist rule, the government stepped up efforts to "cleanse" the internet, blocking access to pornography, Facebook, Twitter, YouTube and various blogs.
Last summer, PC makers were ordered to preload web-filtering software named "Green Dam" to block pornography and banned political sites on all new computers sold in China.
After a domestic and international uproar, the government indefinitely set aside the requirement.
These efforts have swollen the ranks of Chinese involved in a counter-campaign dubbed "fanqiang," or scaling the wall. They use overseas proxy Web sites and VPN, or virtual private network, services to access forbidden material.
"Of course almost everyone has been harmonised; being harmonised is a kind of normal way of life now," said blogger Zhao Jing, whose pen name is Michael Anti.
His website was permanently blocked in 2005 when he advocated boycotting a newspaper after its editors ran afoul of authorities and were sacked.
"More and more censorship is occurring," said Zhao, who now uses Twitter through VPN to advocate freedom of expression but avoids direct challenges to the government, which can land critics in prison.
"If you don't have VPN, you can't do anything on the internet in China. Several years ago if you wanted to have a website you only needed one license. Now you need five to 10 licenses. Censorship is not only about politics - it's about money."
Without a free internet, he added, Chinese are relegated to "second-class citizens in the information society."
Mao, a software architect and researcher in social technology, believes Internet clamp downs will ultimately hurt China's competitiveness in the global economy.
"Censorship harms innovation in China, because people can't as easily access knowledge as their counterparts overseas," he said.