function ff_valid_time_or_empty(element, message)
{
	if(element.value != '') {
		var check = /^(1[012]|[1-9]):[0-5][0-9]$/;
		if (!check.test(element.value)){
			if (message=='') message = element.name+" is not a valid time.\n";
			ff_validationFocus(element.name);
			return message;
		} // if
	} // if
	return '';
} // ff_valid_time_or_empty