function invalidEmail(field){
	var i = 1;
	var sLength = field.value.length;
	if (isEmpty(field))return true;
	while ((i < sLength) && (field.value.charAt(i) != "@"))i++;
	if ((i >= sLength) || (field.value.charAt(i) != "@"))return true;
	else i += 2;
	while ((i < sLength) && (field.value.charAt(i) != "."))i++;
	if ((i >= sLength - 1) || (field.value.charAt(i) != "."))return true;
	return false;
	}