由于IDN的漏洞，firefox把这个功能给改了一下，要改回去，可以按下面的步骤
This is likely due to the translantion of non-Roman characters to punycode.
type about:config in the address bar in the filter box type IDN, double click on
the 'network.IDN_show_punycode' setting to change to false. This should enable
the keyword.
From the 1.0.1 Release notes.
International Domain Names are now displayed as punycode. (To show International
Domain Names in Unicode, set the "network.IDN_show_punycode" preference to
false.)