Ready access to e-mail, blogs, online news, YouTube and other Internet sites is something we take for granted. Except for filtering by parents, schools and libraries, we can click on any site at any time - barring a computer crash or electric blackout. That freedom isn't shared everywhere, and not just because poverty keeps hundreds of millions off-line.

More ominously, officials in tightly controlled places - such as China, Burma and Pakistan - try to censor electronic information about touchy topics. Chinese computer users can't see YouTube or British Broadcasting Co. videos of their government's crackdown on religious freedom rallies in Tibet. Elsewhere in Asia, Burma went further last fall by cutting off all domestic Internet access when it violently suppressed protests by tens of thousands of Buddhist monks. Also in late 2007, Pakistan's leaders moved to prevent YouTube access a few weeks after restricting domestic cable TV news and newspapers.

A just-published book, Access Denied: The Practice and Policy of Global Internet Filtering, says governments block online information in at least 25 countries, including Turkey, Thailand, Iran and Saudi Arabia. Even in Europe, Germany and France won't allow content involving Nazi items and Holocaust denial. Cyber censorship puts Google, Yahoo! and other U.S. technology companies in a squeeze between democratic values and business realities in restrictive lands.

New rules in China: As of this year, all video sites hosted inside China need government licenses and state ownership or investment -- making it easier to shut them down.

Chinese blogger says: "Rulers believe they can build a better system and get others to follow. But even though they want to change the Internet, it is part of a globalized world and nobody can afford to build an isolated system. I believe the internet will change China more than China changes the Internet." -- Isaac Mao, pioneer blogger and researcher

Professor says: "There's tension for these states that are carrying out state-mandated Internet filtering: They want to have the Internet they want and not the Internet they don't. So far that has proven impossible." -- John Palfrey, Harvard University law professor and executive director of the Center for Internet & Society