var how_many_ads = 20;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;
if (ad <= 20) {
txt="";
url="";
alt="";
banner="http://wings.buffalo.edu/intadmit/new/images/left_side/" + ad + ".jpg";
width="172";
height="172";
}

document.write('<center>');
document.write('<a href=\"' + url + '\" target=\"_top\">');
//document.write(ad + " " + now + " " + sec);
document.write('<img src=\"' + banner + '\" width=')
document.write(width + ' height=' + height + ' ');
document.write('alt=\"' + alt + '\" border=0>');
document.write('<small>' + txt + '</small></a>');
document.write('</center>');