var how_many_ads = 4;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;
if (ad==1) {
url='
';
}
if (ad==2) {
url='
';
}
if (ad==3) {
url='
';
}
if (ad==4) {
url='
';
}
document.write('');
document.write(url);
document.write('
');