function getXmlHttp() {
    var xmlHttpObject;
    try {
        // Firefox, Opera 8.0+, Safari
        xmlHttpObject=new XMLHttpRequest();
    } catch (e) {
        // Internet Explorer
        try {
            xmlHttpObject=new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                xmlHttpObject=new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {
                // alert("Your browser does not support AJAX!");
                return null;
            }
        }
    }
    return xmlHttpObject;
}