adImages = new Array("images/pix01.jpg","images/pix02.jpg","images/pix03.jpg","images/pix04.jpg");
thisAd = 0;
imgCt = adImages.length;

function rotate()
{
   if (document.images)
   {
      if (thisAd == imgCt)
      {
         thisAd = 0;
      }
      document.adBanner.src=adImages[thisAd];
      thisAd++;

      setTimeout("rotate()", 4 * 1000);
   }
}