function setBackground(id, xPos, yPos){
  var left = xPos;
  var top = yPos;
  if(document.getElementById) {
    document.getElementById(id).style.backgroundPosition = left+"px "+top+"px";
    document.getElementById(id).style.display= "block";
  } else if(document.all) {
    document.all.id.style.backgroundPosition = left+" "+top;
    document.all.id.style.display = "block";
  }
}

function clearStyle(id) {
  var element = document.getElementById(id);
  element.style.display = "none";
}