Ajax Simple Application

<script language="javascript">
// var http = new XMLHttpRequest();

var http = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");

var url = "13update_lotsize.php";
var params = "";
http.open("GET", url+"?"+params, true);
http.onreadystatechange = function() {//Call a function when the state changes.
if(http.readyState == 4 && http.status == 200) {
//document.write("Update OK");
// alert(http.responseText);
}
}
http.send(null);

</script>