If you live outside of China, you probably don’t have access to the much controversial google.cn because Google redirects you to the mirror site of your country for faster access and options to display only local contents. To test google.cn out, use this address: http://www.google.cn/intl/zh-CN/.
To see the filter in action, try searching for Falun Gong on Google.cn, and compare the results with unfiltered search. On google.cn, when search results have been filtered, you would see the following message at the bottom of the results:
In English, they mean “In accordance with the local law and policies, certain search results have been omitted”.
Excellent article, I was trying to find a way to get access to nasty google. Another very interesting search you can do is to go into image search and search for “tiananmen square”.