function GetXMLHttp() {
        var xmlHttp;
        try {
                xmlHttp = new XMLHttpRequest();
        }
        catch(ee) {
                try {
                        xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
                }
                catch(e) {
                        try {
                                xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                        }
                        catch(e) {
                                xmlHttp = false;
                        }
                }
        }
        return xmlHttp;
}

var xmlRequest = GetXMLHttp();