createXmlHttp

function createXmlHttp() {

    var xmlHttp = null;
    if (typeof XMLHttpRequest != "undefined") {
        xmlHttp = new XMLHttpRequest();
    }
    else if (typeof window.ActiveXObject != "undefined") {
        try {
            xmlHttp = new ActiveXObject("Msxml2.XMLHTTP.4.0");
        }
        catch (e) {
            try {
                xmlHttp = new ActiveXObject("MSXML2.XMLHTTP");
            }
            catch (e) {
                try {
                    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch (e) {
                    xmlHttp = null;
                }
            }
        }
    }
    return xmlHttp;
}