// Mozilla/Safari/IE7+
if (window.XMLHttpRequest) {
        xmlHttpReq = new XMLHttpRequest();
        if(xmlHttpReq.overrideMimeType){                
                xmlHttpReq.overrideMimeType(‘text/xml’);
        }
}
// IE6-
else if (window.ActiveXObject) {
        xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlHttpReq.open(‘POST’, strURL, true);