function showAutor(which) {
  document.getElementById("div" + which).style.visibility = "visible";
  document.getElementById("img" + which).style.visibility = "visible";
  if (which == 5) {
     document.getElementById("div6").style.visibility = "visible";
  }
}
function hideAutor(which) {
  document.getElementById("div" + which).style.visibility = "hidden";
  document.getElementById("img" + which).style.visibility = "hidden";
  if (which == 5) {
     document.getElementById("div6").style.visibility = "hidden";
  }
}

function showImprint(x) {
  var showstring = "hidden";  
  if (x != 0) {
    showstring = "visible";
  }
  var posX = Math.ceil(Math.random() * 800);
  var posY = Math.ceil(Math.random() * 400);
  document.getElementById("imprintlayer").style.left = posX;
  document.getElementById("imprintlayer").style.top = posY;
  document.getElementById("imprintlayer").style.visibility = showstring;
}