Geolocation

if (navigator.geolocation) {
  navigator.geolocation.getCurrentPosition(function(position) {
    var latLng = new google.maps.LatLng(
        position.coords.latitude, position.coords.longitude);
    var marker = new google.maps.Marker({position: latLng, map: map});
    map.setCenter(latLng);
  }, errorHandler);
}