Pakistan's attempts to block access to YouTube have been blamed for a near global blackout of the site on Sunday.
By Jim Reed
Newsbeat technology reporter
It pulled the plug because it said the site featured clips which were offensive to Islam. The ban on YouTube has now been lifted.
But Pakistan isn't the only country in the world which has censored or still censors what people can or cannot read online.
The pressure group Reporters Without Borders calls China "unquestionably the world's most advanced country in internet filtering".
Some big firms have censored themselves for China
Dozens of regulations are designed to stop users accessing a wide variety of illegal content.
A filter, nicknamed the "Great Firewall of China", blocks access to at least 18,000 websites including bbc.co.uk.
Sites relating to political topics like Tibetan independence, police brutality and the 1989 Tiananmen Square protests are impossible to access.
Western companies including News International, Google and Microsoft have been criticised for making some of their products comply with Chinese rules and practices.
The local version of MySpace, for example, removes links to discussion boards dealing with some religious and political topics.
Dozens of Chinese "cyber dissidents" are reportedly in prison after posting criticism of the government online.
Pakistan blocks a small number of websites that display information seen as sensitive or illicit. Pornographic sites are heavily targeted.
The Supreme Court has ordered government departments to block websites showing blasphemous content.
A blanket ban on some blogging and user-generated sites was imposed in 2007 after they were found to contain copies of cartoons of the Prophet Muhammad.
The UK has no specific law censoring internet content.
All major domestic broadband companies pass internet traffic through a filter which identifies sites thought to contain indecent images of children.
The blacklist is put together by an independent organisation called the Internet Watch Foundation.
Germany has some of the toughest laws banning race hate crimes in the world.
Internet providers have been ordered to block access to websites containing neo-Nazi propaganda and other racist material.
It's thought some internet search engines modify their results to remove references to extremist websites.
Egypt allows most websites and carries out "little online filtering", according to Reporters Without Borders.
Abdel's sentence was condemned by human rights groups
A number of bloggers have been arrested.
Some have been held for up to three months in jail after calling for democratic reforms.
Abdel Kareen Nabil Suleiman was sentenced last year to four years in prison for defaming President Hosni Mubarak and insulting religion in an internet message.
Widely seen as the most restricted country in the world in terms of web access.
It's thought that only an elite community of foreigners and government employees have an internet connection.
The country's .nk domain name has never been used.
Its news agency, trade office and official government websites are hosted overseas.
The military regime in Burma is widely thought to filter opposition websites.
Internet access to the country was cut in 2007 in an attempt to stop footage of pro-democracy protests leaving the country.
According to Reporters Without Borders, the government keeps a close eye on internet cafes.
Computers are said to take an automatic picture of the screen every five seconds to monitor and record what users are up to.