function ajax_request(url, params, callback){
    var xmlhttp = false;

    /*@cc_on @*/
    /*@if (@_jscript_version >= 5)
    // JScript gives us Conditional compilation, we can cope with old IE versions.
    // and security blocked creation of the objects.

    try {
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
        try {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (E) {
            xmlhttp =  false;
        }
    }

    @end @*/

    if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
        try {
            xmlhttp = new XMLHttpRequest();
        } catch (e) {
            xmlhttp = false;
        }
    }

    if (!xmlhttp && window.createRequest) {
        try {
            xmlhttp = window.createRequest();
        } catch (e) {
            xmlhttp = false;
        }
    }

    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4) {
            callback(xmlhttp.responseText);
        }
    }

    xmlhttp.open("POST", url, true);
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.setRequestHeader("Content-length", params.length);
    xmlhttp.setRequestHeader("Connection", "close");
    xmlhttp.send(params);
}