CTL censored in China

Thanks to a post by Dr. X, I discovered that this blog is banned in China--at least according to the Great Firewall of China, a site that purports to test any URL to see if it is blocked in China.    I'm interested to know how sites make the blacklist.  That there must be a keyword algorithm or something like that for censoring site--if so, I guess "suicide" or "risk" is on that list.