<apex:page>
<!-- Begin Default Content REMOVE THIS -->
<h1>Welcome </h1> Your Location is

<div id="startLat">
</div>

<div id="startLon">
</div>

<script>
    window.onload = function() {
        var startPos;
        var geoSuccess = function(position) {
            startPos = position;
            document.getElementById('startLat').innerHTML = startPos.coords.latitude;
            document.getElementById('startLon').innerHTML = startPos.coords.longitude;
        };
        navigator.geolocation.getCurrentPosition(geoSuccess);
    };
</script>
</apex:page>