function check_code(user_code) {
	if (ajax) {
		var q = 'validate.php?c=' + encodeURIComponent(user_code);
		ajax.open('get',q,true);
		ajax.onreadystatechange = validate_check;
		ajax.send(null);
	} 
}

function validate_check() {
	if ((ajax.readyState == 4) && (ajax.status == 200)) {
		document.getElementById('user_check').innerHTML = ajax.responseText;
	}
}