The number of Chinese websites fell dramatically last year after the government tightened controls on the Internet, according to a new study by a leading state-run research institute. China has the world\'s biggest online population with 457 million Internet users and the web has become a forum to express opinions in a way rarely seen in the official media. But Beijing also operates some of the world\'s toughest web censorship, with a system known as the \"Great Firewall of China\" blocking access to any content deemed unacceptable. The Chinese Academy of Social Sciences (CASS) said there were 1.91 million websites operating in China at the end of 2010, 41 percent fewer than a year earlier, attributing the change to stronger regulation. \"Although the Internet is posing some problems for new media, our regulation is becoming stronger, we have taken a very big step in this area,\" CASS media expert Liu Ruisheng was quoted as saying on the organisation\'s website. Liu said China had \"a very high level of freedom of online speech\" and there had been few cases in recent years of sites being closed purely to control speech. He said a crackdown launched by the government in 2009 under which thousands of sites were shut down was mainly aimed at putting a stop to online pornography, although critics have said other sites were also closed. But while the number of websites dropped, Liu said Chinese webpages increased in 2010 by 60 billion, an increase of 78.6 percent over 2009. \"This means our content is getting stronger, while our supervision is getting more strict and more regulated,\" he said. Earlier this year, Chinese web police censored Internet calls for Arab-style uprisings in China. This month, the government also censored all postings on China\'s Twitter-like microblog Weibo that referred to former president Jiang Zemin, who is reported to be seriously ill. The government has long viewed the health of the nation\'s top leaders as a state secret, due to concerns illness might affect the political stability in the ruling Communist Party. Numerous overseas Chinese websites, including sites run by exiled political dissidents and rights groups, are blocked inside China, as are popular Internet portals such as Facebook, YouTube and Twitter.