Over on Twitter a China-based blogger has started a list of sites that are currently blocked by China's Great Firewall.

For the last month Twitter-users have been regularly tagging links to sites they find blocked, and unblocked, inside China. It's idea of Shanghai-based blogger and Twitter user Dedric Lam.

Some of the sites reported blocked include news outlets such as the China Digital Times and the USA Today's blog pages. The Tor Project, which allows people to communicate anonymously on the Internet, has also been blocked, as have online virtual community website Live Journal and blogging site Word Press.

Behind China's Great Firewall Chinese authorities censor the websites they don't want Internet users to see. That means they block websites belonging to Western media organisations such as the BBC and human rights groups such as Amnesty International.

But there's no exact list of what is censored or what authorities are looking for – so you never know for sure if the site you are searching for has been blocked or there is just some error with the website or maybe your computer. It's all kept deliberately vague, but it's constantly updated.