function addMarker(map, lat, lng, info) {
  var marker = new GMarker(new GLatLng(lat, lng));
  map.addOverlay(marker);
  GEvent.addListener(marker, "click", function() { marker.openInfoWindowHtml(info) });
}

window.onload = function() {
  if (GBrowserIsCompatible()) {
    var map_element = document.getElementById("map");
    if (map_element) {
      var map = new GMap2(map_element);
      map.addControl(new GLargeMapControl());
      map.addControl(new GMapTypeControl());
      map.setCenter(new GLatLng(51.500152, -0.126236), 4);
      addMarkers(map);
    }
  }
}

window.onunload = function() {
  GUnload();
}