function change_lang(_lang)
{
	var current = location.href;
	
	if (_lang == 'ja')
	{
		// Japanese -> English
		var pattern = /http:\/\/[0-9a-zA-Z\._]*\//;
		var domain = current.match(pattern);
		location.href = current.replace(domain, domain + 'ja/');;
	}
	else
	{
		// English -> Japanese
		location.href = current.replace('ja/', '');
	}
}