function writeBanner(key) {

    if (key == "") { return; }

    var dt = new Date();
    var n = Math.floor(dt.getDay() / 4);

    var b = banner[key];
    if (!b)    { return; }
    if (!b[n]) { return; }
    document.write('<a href="' + b[n].url + '" border="0"><img src="' + b[n].src + '" border="0" /></a>');
}