You can also do it with javascript based on browser language setting. I use it to filter out Chinese traffic.
Code:
<SCRIPT TYPE="text/javascript" LANGUAGE="JavaScript">
if (navigator.appName == 'Netscape')
var language = navigator.language;
else
var language = navigator.browserLanguage;
if (language.indexOf('zh') > -1 || language.indexOf('zh-cn') > -1 || language.indexOf('zh-hk') > -1 || language.indexOf('zh-mo') > -1 || language.indexOf('zh-tw') > -1 || language.indexOf('zh-sg') > -1)
document.location.href = 'http://www.insert-your-redirect-url-here.com';
</script>