var how_many_ads = 4;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;
if (ad==1) {
banner="images/banner-index1.jpg";
}
if (ad==2) {
banner="images/banner-index2.jpg";
}
if (ad==3) {
banner="images/banner-index3.jpg";
}
if (ad==4) {
banner="images/banner-index4.jpg";
}


document.write('<img src=\"' + banner +'\" alt=\"Banner\" width=\"980\" height=\"200\" border=\"0\" />');