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<html>
<head>
<script type="text/javascript">
var xmlhttp;
function loadXMLDoc(url)
{
xmlhttp=null;
if (window.XMLHttpRequest)
  {// code for Firefox, Mozilla, IE7, etc.
  xmlhttp=new XMLHttpRequest();
  }
else if (window.ActiveXObject)
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
if (xmlhttp!=null)
  {
  xmlhttp.onreadystatechange=state_Change;
  xmlhttp.open("GET",url,true);
  xmlhttp.send(null);
  }
else
  {
  alert("Your browser does not support XMLHTTP.");
  }
}

function state_Change()
{
if (xmlhttp.readyState==4)
  {// 4 = "loaded"
  if (xmlhttp.status==200)
    {// 200 = "OK"
    document.getElementById('p1').innerHTML=xmlhttp.getAllResponseHeaders();
    }
  else
    {
    alert("Problem retrieving data:" + xmlhttp.statusText);
    }
  }
}
</script>
</head>
<body>

<pre id="p1">
The getAllResponseHeaders() function returns the headers of a resource.
The headers contain file information like length,
server-type, content-type, date-modified, etc.</pre>

<button onclick="loadXMLDoc('/example/xdom/test_xmlhttp.txt')">Get Headers</button>

</body>
</html>

W3School TIY Editor