I have tried your solution guys become like this :
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml">
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
<title>Google Maps JavaScript API Example: Extraction of Geocoding Data</title>
<script>
function gcd()
{
var getlong1 = document.getElementById("long1").value;
var getlat1 = document.getElementById("lat1").value;
var getlong2 = document.getElementById("long2").value;
var getlat2 = document.getElementById("lat2").value;
var long1 = parseFloat(getlong1);
var lat1 = parseFloat(getlat1);
var long2 = parseFloat(getlong2);
var lat2 = parseFloat(getlat2);
var R = 6371;
var a1 = lat1.toRadians();
var a2 = lat2.toRadians();
var Δφ = (lat2-lat1).toRadians();
var Δλ = (long2-long1).toRadians();
var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
Math.cos(a1) * Math.cos(a2) *
Math.sin(Δλ/2) * Math.sin(Δλ/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
document.getElementById('results').innerHTML = d;
return d;
}
</script>
</head>
<body>
<form action="#" onsubmit="gcd(); return false;">
<p>
Lokasi 1 :
<input type="text" name="long1" id="long1" size="40" />
<input type="text" name="lat1" id="lat1" size="40" />
</p>
<p>
Lokasi 2 :
<input type="text" name="long2" id="long2" size="40" />
<input type="text" name="lat2" id="lat2" size="40" />
</p>
<p>
<input type="submit" name="find" value="Search" />
</p>
</form>
<p id="results"></p>
</body>
</html>
But it still can't work :(