function isValidURL(u) {     
	var r = u.match(/^(ht|f)tps?:\/\/[a-z0-9-\.]+\.[a-z]{2,4}\/?([^\s<>\#%"\,\{\}\\|\\\^\[\]`]+)?$/);
	if(r == null) return false;
	return true;
}

function updateDomainCheck(u, t) 
{
	var www = u.toLowerCase().indexOf('www.');
	if(www == 0) {
		u = u.substr(4);
		t.value = u;
	}

	var el = document.getElementById('checkout');
	if(isValidURL('http://'+u)) {
		el.className = 'checkout_ok';
	} else {
		el.className = 'checkout';
	}
}