http://static.4chan.org/image/flags.png

There are two off-center flags, Switzerland and Nepal. They're 11x11 and 9x11, respectively, so they can't be correctly centered in the 16x11 flag space. To fix this, just give the .flag-ch class a width:11px and the .flag-np class a width:9px to override the .flag class default of width:16px.