function swapAds() {
  if(document.getElementById) {
    // set up the paused effect
    mainDiv = document.getElementById('directory-2008treasurehunt');
    heading = document.getElementById('directory-2008treasurehunt-heading');
    mainDiv.onmouseover = pauseAds;
    mainDiv.onmouseout = resumeAds;
    // set up and start the script
    var prizes = document.getElementById('directory-2008treasurehunt-prizes');
    var advertisers = document.getElementById('directory-2008treasurehunt-advertisers');
    if(prizes && advertisers) {
      // add the classes for the stylesheet to hook into
      prizes.className = 'directory-2008treasurehunt-prizes-js';
      advertisers.className = 'directory-2008treasurehunt-advertisers-js';

      // make a list of prizes and ads
      prizeList = listChildElements(prizes);
      advertiserList = listChildElements(advertisers);
      
      // show the first ad
      okToContinue = true;
      var current = 0;
      if(prizeList[current])
        prizeList[current].className = 'current';
      if(advertiserList[current])
        advertiserList[current].className = 'current';

      // preload the 'paused' image
      (new Image()).src = 'images/treasure_hunt_prizes_paused.gif';

      // set the ads going
      window.setTimeout('showNextAd('+current+')', 3000);
    }
  }
}


function showNextAd(current) {
  if(okToContinue) {
    if(prizeList[current])
      prizeList[current].className = '';
    if(advertiserList[current])
      advertiserList[current].className = '';
    current++;
    if(current>=prizeList.length && current>=advertiserList.length)
      current = 0;
    if(prizeList[current])
      prizeList[current].className = 'current';
    if(advertiserList[current])
      advertiserList[current].className = 'current';
  }
  window.setTimeout('showNextAd('+current+')', 3000);
}


function listChildElements(parent) {
  var list = new Array();
  for(var i=0; i<parent.childNodes.length; i++) {
    if(parent.childNodes[i].nodeType==1  // Node.ELEMENT_NODE
       && parent.childNodes[i].tagName.toLowerCase()=='li') {
      // add this element to the list
      list[list.length] = parent.childNodes[i];
    }
  }
  return list;
}


function pauseAds() {
  okToContinue = false;
  mainDiv.className = 'directory-2008treasurehunt-paused';
  heading.firstChild.src = 'images/treasure_hunt_prizes_2008_paused.gif';
}


function resumeAds() {
  heading.firstChild.src = 'images/treasure_hunt_prizes_2008.gif';
  mainDiv.className = '';
  okToContinue = true;
}


swapAds();