At first, Liu Xiao-yuan just fumed when his online journal postings disappeared with no explanation. Then he decided to do something few, if any, of China's censored bloggers had tried. He sued his service provider.
"Each time I saw one of my entries blocked, I'd feel so furious and indignant," said Liu, 43, a Beijing lawyer. "It was just so disrespectful."
Liu's frustration is hardly unique. For China's 162 million web users, surfing the Internet can be like running an obstacle course with blocked websites, partial search results and posts disappearing at every turn.
Blog entries such as Liu's, which mused on sensitive topics such as the death penalty, corruption and legal reform, are often automatically rejected if they trigger a keyword filter.
Sometimes, they're deleted by human censors employed by Internet companies.
In the lead-up to the sensitive Communist Party Congress, which convened to approve top leaders who will serve under President Hu Jintao until 2012, authorities have been casting an even wider net than usual in their search for Web content they deem to be politically threatening or potentially destabilising.
"What you see now is unprecedented," said Xiao Qiang, director of the China Internet Project at the University of California, Berkeley. "They are forcing most of the interactive sites to simply close down and have unplugged Internet data centres. These are things they haven't done before."
Thousands of sites suddenly went offline in August and September when Internet data centres, which host web servers, were shut down.
In three cities, some services were temporarily cut off, while some interactive websites remain unplugged until after the congress.
It's not uncommon for authorities to crack down on public opinion before party congresses, which are held every five years.
In an increasingly wired China, political rumours and speculation that used to end up in Hong Kong's more liberal media are now often found circulating first in Chinese cyberspace.
At the party congress, there's plenty of opportunity for commentary, speculation and gossip.
The government has built a patchwork system of controls that include software to root out offensive keywords and block blacklisted websites.
Government censors, or "net nannies", surf the web looking for pornography, subversive political content or other illegal material. Major Internet portals such as Sohu.com and Sina employ their own censors to help maintain government restrictions.
China is among a handful of countries that have extensive filters for political sites. Iran, Myanmar, Syria, Tunisia and Vietnam also strictly block political content, according to the OpenNet Initiative, a collaboration between researchers at Cambridge, the University of Oxford, Harvard University and the University of Toronto.
In a report last week, Reporters Without Borders said China's Internet censorship was "unparallelled anywhere in the world" and insulted "the spirit of online freedom".
Commercial sites that don't comply with censorship orders are criticised, fined, forced to fire the employee responsible for the error, or closed down, the Paris-based group said. A point system is also used to keep track of compliance, with sites that rack up a certain number of demerits at risk of losing their business licences.
To underscore its determination, the government also imprisons people who mail, post online, or gain access to politically sensitive content within China. Reporters Without Borders says 50 Chinese "cyber dissidents" are in prison.