var ROTATION_TIME = 5;
var shoppingLinks = [
 {
    'url':    'http://www.cafepress.com/petastore.163344715',
    'imgUrl': '/buttons/abc_dog_teeshirt.jpg',
    'text':   'Animal Birth Control<br>Dog T-Shirt'
  },
  {
    'url':    'http://www.cafepress.com/petastore.197504894',
    'imgUrl': '/buttons/mean_people_breed_dogs_teeshirt.jpg',
    'text':   'Mean People Breed Dogs<br>Women&rsquo;s Cap Sleeve T-Shirt'
  },
   {
    'url':    'https://www.petacatalog.org/prodinfo.asp?internal=y&number=BS812',
    'imgUrl': '/buttons/i_heart_my_mutt_sticker.jpg',
    'text':   '&lsquo;I (Heart) My Mutt&rsquo; Sticker'
  },
  {}
];
var preloadedImages = [];
var adIndex = 0;
function generateShoppingLink()
{
//  var adIndex = Math.floor(Math.random() * shoppingLinks.length - 1);
  var adHtml = '<a href="'+ shoppingLinks[adIndex].url +'" target="_blank">'+
               '<img src="'+ preloadedImages[adIndex].src +'" border="0" style="border: 1px #ccc solid;" /></a>'+
               '<br /><a href="'+ shoppingLinks[adIndex].url +'" target="_blank">'+
               shoppingLinks[adIndex].text +'</a>';
  document.getElementById('shoppingLinkBlock').innerHTML = adHtml;
}
function rotateShoppingLink()
{
  if (adIndex > shoppingLinks.length - 2)
    adIndex = 0;
  generateShoppingLink();
  adIndex++;
  setTimeout("rotateShoppingLink()", (ROTATION_TIME * 1000));
}
function initShoppingLink()
{
  for (var i = 0; i < shoppingLinks.length; i++)
  {
    if (shoppingLinks[i].imgUrl)
    {
      var img = new Image();
      img.src = shoppingLinks[i].imgUrl;
      preloadedImages[i] = img;
    }
  }
  rotateShoppingLink();
}