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This is a step by step guide on how to unblock your website for visitors in China without them having to do anything. The Great FireWall of China is a complicated filtering system capable of blocking websites by a variety of methods. The common methods used are IP blocking, URL and Packet filtering by connection reset, TLS (SSL) certificate filtering by connection reset and DNS hijacking.
IP blocking
Use CDN (Count Delivery Network) to hide the real IP of your site from GFW. I did a simple test myself. I created a Google site and linked it with 4 subdomains as follows.
CNAME records: (ghs.google.com is currently not blocked in China)
test1.example.com -> ghs.google.com CDN enabled
test2.example.com -> ghs.google.com
A records: (216.239.32.21 is subject to IP blocking in China)
test3.example.com-> 216.239.32.21 CDN enabled
test4.example.com -> 216.239.32.21