function http() {
    var h;
    if (typeof(XMLHttpRequest) != "undefined") {
        h = new XMLHttpRequest();
    } else {
        try { h = new ActiveXObject("Msxml2.XMLHTTP"); }
        catch (e) {
            try { h = new ActiveXObject("Microsoft.XMLHTTP"); }
            catch (E) { alert("Your browser is not supported."); }
        }
    }
    return h
}

function http_action(callback) {
    var h = http();
    h.onreadystatechange = function() {
        if (h.readyState == 4) {
            if (h.status != 200 && h.status != 204
                // Internet Explorer may return 1223 for 204
                && h.status != 1223) {
                alert("Error. Status = " + h.status + "\n" + h.responseText);
            } else {
                var result = "";
                var ct = h.getResponseHeader("Content-Type");
                if (ct.split(";")[0] == "text/xml") {
                    try {
                        result = h.responseXML;
                        if (xmldoc == null) throw "No XML in response";
                    } catch (e) {
                        result = h.responseText;
                        alert(h.responseText);
                        return;
                    }
                } else {
                    result = h.responseText;
                }
                if (callback != undefined) callback(result);
            }
        }
    }
    return h;
}