var req;

function loadXMLDoc(url) {
    // branch for native XMLHttpRequest object
    if (window.XMLHttpRequest) {
        req = new XMLHttpRequest();
        req.onreadystatechange = processReqChange;
        req.open("GET", url, true);
        req.send(null);
    // branch for IE/Windows ActiveX version
    } else if (window.ActiveXObject) {
        req = new ActiveXObject("Microsoft.XMLHTTP");
        if (req) {
            req.onreadystatechange = processReqChange;
            req.open("GET", url, true);
            req.send();
        }
    }
}

function processReqChange() {
    if (req.readyState == 4) {
        //if (req.status == 200) {
            var response  = req;
            readResponse(response);
        //} else {
        //    alert("There was a problem retrieving the XML data:\n" + "Status: " + req.status + "\n" + req.responseText);
        //}
    }
}