var newBanner = 0;
var totalBan = bannerImg.length;

function cycleBan() {
  newBanner++;
  if (newBanner == totalBan) {
    newBanner = 0;
  }
  document.banner.src=bannerImg[newBanner];
  // 4 = number of seconds
  setTimeout("cycleBan()", 3*1000);
}
window.onload=cycleBan;