[JavaScript] Funktion läd nicht

var marker;
var infoWindow = new google.maps.InfoWindow();
var form = "<p>Name: <input type='text' id='name' /></p>" +
"<p>Notiz: </p>" +
"<div><textarea name='note' cols='20' rows='5'></textarea></div>" +
"<p><input type='button' value='Speichern' onclick='saveData()' /></p>";
function load() {
 var map = new google.maps.Map(document.getElementById("map"), {
 center: new google.maps.LatLng(53.75, 9.65),
 zoom: 13,
 mapTypeId: 'roadmap'
 });
 downloadUrl("xml.php", function(data) {
 var xml = parseXml(data);
 var markers = xml.documentElement.getElementsByTagName("marker");
 for (var i = 0; i < markers.length; i++) {
 var name = markers[i].getAttribute("name");
 var note = markers[i].getAttribute("note");
 var html = "<b>" + name+ "</b><br />" + note;
 var point = new google.maps.LatLng(
 parseFloat(markers[i].getAttribute("lat")),
 parseFloat(markers[i].getAttribute("lng")));
 var marker = new google.maps.Marker({
 map: map,
 position: point
 });
 bindInfoWindow(marker, map, infoWindow, html);
 }
 });
 google.maps.event.addListener(map, "click", function(event) {
 marker = new google.maps.Marker({
 position: event.latLng,
 map: map
 });
 bindInfoWindow(marker, map, infoWindow, form);
 });
 }
 function bindInfoWindow(marker, map, infoWindow, html) {
 google.maps.event.addListener(marker, 'click', function() {
 infoWindow.setContent(html);
 infoWindow.open(map, marker);
 });
 }
 function downloadUrl(url, callback) {
 var request = window.ActiveXObject ?
 new ActiveXObject('Microsoft.XMLHTTP') :
 new XMLHttpRequest;

 request.onreadystatechange = function() {
 if (request.readyState == 4) {
 request.onreadystatechange = doNothing;
 callback(request.responseText, request.status);
 }
 };
 request.open('GET', url, true);
 request.send(null);
 }
 function saveData() {
 var name = escape(document.getElementById("name").value);
 var note = escape(document.getElementById("note").value);
 var latlng = marker.getPosition();
 var url = "addmarker.php?name=" + name +
 "&note=" + note + "&lat=" + latlng.lat() + "&lng=" + latlng.lng();
 request.open('GET', url, true);
 request.send(null);
 infowindow.close();
 document.getElementById("message").innerHTML = "Location added.";
 }
 function parseXml(str) {
 if (window.ActiveXObject) {
 var doc = new ActiveXObject('Microsoft.XMLDOM');
 doc.loadXML(str);
 return doc;
 } else if (window.DOMParser) {
 return (new DOMParser).parseFromString(str, 'text/xml');
 }
 }

 function doNothing() {}