function getObj(name) {
  if (document.getElementById) {
    return document.getElementById(name);
  }
  else if (document.all) {
    return document.all[name];
  }
  else if (document.layers) {
    return document.layers[name];
  }
}

function set_center() {
  x = getObj('div_map');
  x.style.top = (screen.height - 440) / 2 + "px";
  x.style.left = (screen.width - 520) / 2 + "px";
}

function show_map(url) {
  set_center();
  x = getObj('map_frame');
  x.src = url;
  x = getObj('div_map');
  x.style.display = "block";
}

function close_map() {
  x = getObj('div_map');
  x.style.display = "none";
}