Display Random Ad (WordPress or HTML)

random-ad.html

<script type="text/javascript">
  var total_images = 3;
  var random_number = Math.floor((Math.random()*total_images));
  var random_img = new Array();
  random_img[0] = '<a href="http://google.com"><img src="http://domain.com/images/ad1.gif"></a>';
  random_img[1] = '<a href="http://google.com"><img src="http://domain.com/images/ad2.gif"></a>';
  random_img[2] = '<a href="http://google.com"><img src="http://domain.com/images/ad3.gif"></a>';
  document.write(random_img[random_number]);
</script>