No Twitter, Flickr in China

Less than two days before the 20th anniversary of the Tiananmen Square crackdown, China's cyberpolice blocked the micro-blogging service Twitter.

Internet experts note that a Chinese tweet can have three times the volume of an English tweet, due to the high information intensity of the Chinese language. Around 140 Chinese characters can make up all the full elements of a news piece.

Incidentally, photo-sharing website Flickr.com too has been blocked, and so has Bing.com (the new Microsoft search engine). Live.com and Hotmail.com were already under the scanner, while Blogspot (for blogs) and Youtube (a Google property) remain blocked.

Internet censorship in the People's Republic of China is nothing new. There are over 60 internet regulations. The size of the internet police, according to Wikipedia, is estimated at over 30,000.

Critical comments appearing on internet forums, blogs, and major portals such as Sohu and Sina are usually erased within minutes. Amnesty International notes that China 'has the largest recorded number of imprisoned journalists and cyber-dissidents in the world.'

Moreover, the Golden Shield Project (which makes China the world's No 1 electronic police state, according to Cryptohippie Inc, was started in 1998. The project is also known as the Great Firewall of China (refers both to its role as a network firewall and to the ancient Great Wall of China).

The system blocks content by preventing IP addresses from being routed through and consists of standard firewalls and proxy servers at the internet gateways.

Censored websites in China include the 2008 Summer Olympics website (partial censorship), websites related to Tiananmen Square protests of 1989 and Dalai Lama and his International Tibet Independence Movement, including his teachings.

Blocked websites are indexed to a lesser degree, if at all, by some Chinese search engines, such as Baidu and Google China. A Harvard study notes that at least 18,000 websites are blocked from within China.