China's great firewallThe Chinese government actively blocks certain websites and keywords. ISPs or connection provider (hotel, company, ...) might have their own additional websites or applications that are not allowed.
The government actively blocks foreign social media and news related to 'sensitive' topics. Based on my own experiences the following websites are blocked by the Chinese firewall:
- Google: plus.google.com (only web access, android app access is OK), docs.google.com (web & app blocked)
- www.facebook.com (web & app access blocked)
- Direct links to files from dropbox, however desktop app, android app & web access works
- Links to files from yousendit.com
A great resource is the website Online Censorship in China. You can see which services and websites are blocked.
Webmasters are held responsible for the content that appears on their websites and as such are expected to self-censor the content. This is applicable to all types of content (text, photos, video's, micro-blog, ...)
People in the PRC often circumvent these restrictions by using VPN's or proxies. A good application is Tor, others are JonDonym or Ultrasurf.