var url = "check_availability.asp?id="; // The server-side script
function handleHttpResponse() {   
if (http.readyState == 4) {
	  if(http.status==200) {
		  var results=http.responseText;
	  document.getElementById('divCustomerInfo').innerHTML = results;
	  }
	  }
}

function requestCustomerInfo() {     
	var sId = document.getElementById("txtCustomerId").value;
	http.open("GET", url + escape(sId), true);
	http.onreadystatechange = handleHttpResponse;
	http.send(null);
}
function getHTTPObject() {
  var xmlhttp;

  if(window.XMLHttpRequest){
    xmlhttp = new XMLHttpRequest();
  }
  else if (window.ActiveXObject){
    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    if (!xmlhttp){
        xmlhttp=new ActiveXObject("Msxml2.XMLHTTP");
    }
   
}
  return xmlhttp;
 
}
var http = getHTTPObject(); // We create the HTTP Object