var active_button = "";
//document.images[2].src = "/_images/buttons/click.gif";

function activate(id){
  if (id != active_button && active_button!="")
    document.images[''+active_button].src = "/_images/out.gif";
  document.images[''+id].src = "/_images/click.gif";
  active_button=id;
}


function premark(id){
  if (id != active_button)
    document.images[''+id].src = "/_images/over.gif";
}

function unmark(id){
  if (id != active_button)
    document.images[''+id].src = "/_images/out.gif";
}