function clearMarker() {
 document.getElementById('marker').style.display = 'none';
}

function setMarker(x, y) {
 if (x <= 412 && y <= 552) {
  document.getElementById('marker').style.display = 'block';
  document.getElementById('marker').style.padding = y + 'px 0 0 ' + x + 'px';
 }
}