The local DNS you use in China is probably contaminated
and popular sites like Google, Facebook, etc. are not interpreted correctly.
So if you are in China and use Firefox with Proxy,
make sure to set network.proxy.socks_remote_dns to be true (follow steps below).
-
Open an empty tab in Firefox.
-
Go to about:config in the URL bar.
-
Search for
network.proxy.socks_remote_dns. -
Change the value to be
true.