function startMap(strParameter) {
  var request = GXmlHttp.create();
  request.open("GET", "locations.aspx?" + strParameter , true);
  request.onreadystatechange = function() {

  if (request.readyState == 4) {
    var xmlDoc = request.responseXML;
    var markers = xmlDoc.documentElement.getElementsByTagName("marker");

    for (var i = 0; i < markers.length; i++) {
      var mpoint = new GPoint(
          markers[i].getElementsByTagName("lng")[0].firstChild.nodeValue,
          markers[i].getElementsByTagName("lat")[0].firstChild.nodeValue
      );

      var marker = createMarker(mpoint, i);
      map.addOverlay(marker);
    }
  }
}