// This function creates a cross-browser AJAX object
function GetXmlHttp() {
    var xmlHttp;
    try { xmlHttp = new XMLHttpRequest(); } // Firefox, Opera 8.0+, Safari
    catch (e) {
        try { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } // IE 6.0+
        catch (e) {
            try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } // Older IE
            catch (e) {
                alert("Your browser does not support AJAX!");
                return false;
            }
        }
    }
    return xmlHttp;
}