var xmlHttp

function checkNumber(num)
{
if (num.length==0)
{ 
document.getElementById("zip_results").innerHTML=""
return
}
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request")
return
} 
/*  Here are the possible values for the readyState property:

State Description 
0 The request is not initialized 
1 The request has been set up 
2 The request has been sent 
3 The request is in process 
4 The request is complete

php do not cache page header
header("Cache-Control: no-cache, must-revalidate");

var url="gethint.php"
url=url+"?q="+str
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged 
xmlHttp.open("GET",url,true)
xmlHttp.send(null)*/

var url="zipcode.php"
url=url+"?n="+num
url=url+"&sid="+Math.random()//attaching a random number to the end of the url keeps the server from using a cached page
xmlHttp.onreadystatechange=stateChanged 
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
} 

function stateChanged(){ 
	if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ 
		document.getElementById("zip_results").innerHTML=xmlHttp.responseText 
	}else if(xmlHttp.readyState==3){
		document.getElementById("zip_results").innerHTML="Searching..."
	}
} 

function GetXmlHttpObject()
{
  var xmlHttp=null;
  try
    {
    // Firefox, Opera 8.0+, Safari
    xmlHttp=new XMLHttpRequest();
    }
  catch (e)
    {
    // Internet Explorer
    try
      {
      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
    catch (e)
      {
      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    }
  return xmlHttp;
}