// from http://jibbering.com/2002/4/httprequest.html :
var xmlhttp=false;

function init_xmlhttp() {
    /*@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') {
        xmlhttp = new XMLHttpRequest();
    }
}

function update_bar() {
    if (xmlhttp.readyState == 4) {
        var obj = eval(xmlhttp.responseText);
        var elem = document.getElementById(obj.x);
        // TODO: retrieve contained elements by name and change their heights instead?
        elem.innerHTML = "<div class='fil' style='height:" + (100 - obj.y) + "%'>&nbsp;</div>" +
                         "<div class='bar' style='height:" + obj.y + "%'>&nbsp;</div>";
    }
}

function get_value(url) {
    xmlhttp.open("GET", url, true);
    xmlhttp.onreadystatechange = update_bar;
    xmlhttp.send(null);
}

function update_chart(id) {
    if (!xmlhttp)
        alert("No XmlHttp object!");
    else
        get_value("?id=" + id + "&a=count");
}