function imageswap_over(button_id, ext)
{
  var button_obj;

  if (document.getElementById) {
    button_obj = document.getElementById(button_id);
  } else {
    button_obj = document[button_id];
  }

  img_name = "./images/" + button_id + "_over" + ext;

  button_obj.src=img_name;

}


function imageswap_out(button_id, ext)
{
  var button_obj;

  if (document.getElementById) {
    button_obj = document.getElementById(button_id);
  } else {
    button_obj = document[button_id];
  }

  img_name = "./images/" + button_id + ext;

  button_obj.src=img_name;
}