function popup_window(url,w,h) 
{
  
  if (!w)
  {
    w = 380;
  }
  if( !h)
  {
    h = 680;
  }
  var left=parseInt((screen.availWidth/2)-(w/2));
  var top=parseInt((screen.availHeight/2)-(h/2));
  
  window.open(url, 'popup', 'width='+w+', height='+h+', menubar=no, scrollbar=yes, toolbar=no, location=no, resizable=no, top='+top+', left='+left);
}