function get_xmlhttp(){
    var r;
    try {
        r = new XMLHttpRequest();
    } catch(e) {
        var c = new Array('MSXML2.XMLHTTP.5.0','MSXML2.XMLHTTP.4.0','MSXML2.XMLHTTP.3.0','MSXML2.XMLHTTP','Microsoft.XMLHTTP');
        c_length = c.length;
        for(var i=0; i<c_length && !s; i++) {
            try {  r = new ActiveXObject(c[i]); } catch(e) { }
        }
    }
    return r;
}

function ajax_open(s) {
    xmlhttp = get_xmlhttp();
    xmlhttp.open("GET", s, false);
    xmlhttp.send(null);
    return xmlhttp.responseText
}