window.onload = rotate;

var thisAd = 0;

function rotate() {
     var adImages = new Array("assets/one.jpg","assets/two.jpg","assets/three.jpg");

     thisAd++;
     if (thisAd == adImages.length) {
        thisAd = 0;
     }
     document.getElementById("adBanner").src =adImages[thisAd];

     setTimeout(rotate, 3 * 1400);
}