// callback is of the form:
//     callback(responseXml)
function xmlHttpPost2(strURL,contentStr,isAsync,callback) {
    var xmlHttpReq = false;
    // Mozilla/Safari
    if (window.XMLHttpRequest) {
        xmlHttpReq = new XMLHttpRequest();
		if(xmlHttpReq.overrideMimeType)
			xmlHttpReq.overrideMimeType('text/xml');
    }
    // IE
    else if (window.ActiveXObject) {
        xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlHttpReq.open('POST', strURL, isAsync);
    xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xmlHttpReq.onreadystatechange = function() {
        if (xmlHttpReq.readyState == 4) {
            callback(xmlHttpReq.responseXML);
        }
    }
    xmlHttpReq.send(contentStr);
}