var xmlHttp;
function createXMLHttpRequest() {
       if (window.ActiveXObject) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
       }
       else if (window.XMLHttpRequest) {
            xmlHttp = new XMLHttpRequest();
       }
}

function getXMLDocument() {
    var xRequest = null;
    if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    } else if (typeof ActiveXObject != "undefined") {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return xmlHttp;
}