window.onload=choosePic;

var adImages=new Array("images/index_17.gif","images/index_17_1.gif","images/index_17_2.gif","images/index_17_3.gif","images/index_17_4.gif");
var thisAd=0;

function rotate() {
   thisAd++;
   if(thisAd==adImages.length) {
      thisAd=0;
   }
   document.getElementById("adBanner").src=adImages[thisAd];
   setTimeout("rotate()",3*1000);
}  

function choosePic() {
	thisAd=Math.floor(Math.random()*adImages.length);
	document.getElementById("adBanner").src=adImages[thisAd];
	rotate();
}