[kilohertz_.]

<script type="text/javascript">
		var xml;
		function formSend() {
			xml = new XMLHttpRequest();
			xml.open("POST","ajax/register.php",true);
			xml.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
			var name = '', mail = '', phone = '', password = '', password_d = '';
			name = document.getElementsByName("name")[0].value;
			mail = document.getElementsByName("mail")[0].value;
			phone = document.getElementsByName("phone")[0].value;
			password = document.getElementsByName("password")[0].value;
			password_d = document.getElementsByName("password_d")[0].value;
			xml.onreadystatechange = process;
			xml.send('name='+name+'&mail='+mail+'&phone='+phone+'&password='+password+'&password_d='+password_d+'&who=');		
		}
		
		function process() {
			if(xml.readyState == 4) {
				var resp = xml.responseXML;
				var text = resp.getElementById("res").firstChild.nodeValue;
				alert(text);
			}
		}
	</script>

Почему выдает Uncaught TypeError: Cannot read property 'getElementById' of null в строчке var text = resp.getElementById("res").firstChild.nodeValue;? Где ошибка?