Here's a sample XMLHttpRequest I cobbled together from w3schools

<html>
<head>
<script type="text/javascript">
function loadXMLDoc()
{
  var T="nothing";

  xmlhttp=new XMLHttpRequest();
  xmlhttp.overrideMimeType('text/plain');  // don't sc
  xmlhttp.onreadystatechange=function()
  {
    alert ("rdystate: " + xmlhttp.readyState);
    alert ("status: "   + xmlhttp.status);
    alert ("Text: "     + xmlhttp.statusText);
    if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
      T = xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","SBL_PROBES.htm",true);
xmlhttp.send(null);
//T = xmlhttp.responseText;
alert(T);
}
</script>
</head>
<body>

<h2>Using the XMLHttpRequest object</h2>
<div id="myDiv"></div>
<button type="button" onclick="loadXMLDoc()">CHange Content</button>

</body>
</html>

XMLHttpRequest always returns a zero status.

Nothing shows up in Firefox's error console.

If I change the request to synchronous one by changing the line

xmlhttp.open("GET","SBL_PROBES.htm",true);

to

xmlhttp.open("GET","SBL_PROBES.htm",false);

and un-comment the line 

//T = xmlhttp.responseText;

The text of the requested file is returned.

The HTM and the file reside in the same directory. If you try this you will need a file SBL_PROBES.htm there also, it's contents are irrelevant.

I'm using Firefox 3.6.22.

Could this be a cross domain problem? If so, why does it work as a synchronous request?

javascript xmlhttprequest
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