var w;
var w_opened = 0;
function popup_popup(url,wi,he) {
  close_popup();
  w=window.open(url,"_blank",xywh(wi,he)+",scrollbars=1,resizable=1");
  w_opened = 1;
}
function close_popup() {
  if (w_opened) {
    w.close();
    w_opened = 0;
  }
}
function xywh(wi,he) {
  if (!wi) wi = screen.width * 2 /3;
  if (!he) he = screen.height * 2 /3;
  var x=(screen.width-wi)/2;
  var y=(screen.height-he)/2;
  return "width="+wi+",height="+he+",screenX="+x+",screenY="+y+",left="+x+",top="+y;
}

function on_close() {
  close_popup();
}

if (navigator.appName == 'Microsoft Internet Explorer') {
  window.onbeforeunload = on_close;
}
else {
  window.onunload = on_close;
}