HTML5 Geolocation with Google Map API V3

gistfile1.html

<div id="map-big" style="width:500px; height:300px"></div>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script>
<script type="text/javascript">
    var locations = [
      ["Tanglin", 1.29559, 103.825607, 3],
      ["Orchard Turn", 1.30431, 103.831905, 2],
      ["Cityhall", 1.29308, 103.852226, 1],
      ];

    if (navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(function(position) {
            showMap(position.coords.latitude, position.coords.longitude);
        });
    }

    else {

    }

    function showMap(geolat, geolng) {

          var map = new google.maps.Map(document.getElementById('map-big'), {
          zoom: 10,
          center: new google.maps.LatLng(geolat, geolng),
          mapTypeId: google.maps.MapTypeId.ROADMAP
        });

        var infowindow = new google.maps.InfoWindow({
            maxWidth: 200
        });

        var marker, i;

        for (i = 0; i < locations.length; i++) {
          marker = new google.maps.Marker({
            animation: google.maps.Animation.DROP,
            position: new google.maps.LatLng(locations[i][1], locations[i][2]),
            map: map
          });

          google.maps.event.addListener(marker, 'click', (function(marker, i) {
            return function() {
              infowindow.setContent(locations[i][0]);
              infowindow.open(map, marker);
            }
          })(marker, i));
        }
    }
</script>

doesn't work