China filters some Google searches

But that end-run doesn't prevent China's government from using its Internet filters — known as the Great Firewall — to block some search results and Web sites from being seen in the mainland.

On Tuesday, a search request from within mainland China about the 1989 Tiananmen democracy protests returned a notice that the "page cannot be displayed." It also caused the Web browser to disconnect for several seconds. Under the old google.cn, a similar query usually returned a list of sanitized sites about Tiananmen Square.

If the Chinese leaders really want to foil Google, they could block all mainland access to the Hong Kong service. Or they could exert their control of Chinese telecommunications companies to slow the speed of queries and responses, to help drive traffic to homegrown rivals.