function create_background(obj){
  obj.style.backgroundImage = "url(citrus/citrus_small.png)";
  obj.style.backgroundPosition = "top left";
  obj.style.backgroundRepeat = "no-repeat";

  // delete image from LastModified
  document.getElementById("last_modified").style.backgroundImage = "none";
}

function delete_background(obj){
  obj.style.backgroundImage = "none";
  document.getElementById("last_modified").style.backgroundImage = "url(citrus/citrus_h2.png)";
}