function arm_download_links() {
  var links;
  divs = document.getElementsByTagName("div");
  var x;
  var link;
  for(x in divs) {
    if(divs[x].className == "download") {
      link = divs[x].firstChild;
      while(link.nodeType == 3) {
        link = link.nextSibling;
        }
      
      link.onclick = disable_download;
      }
    }
  }

function disable_download() {
  var target;
  target = this.href;
  this.parentNode.innerHTML = "<img src='thank_you.jpg' />";
  window.location = target;
  }