function target_blank(url, width, height)
{
  wasOpen = false;
  var top = (screen.availWidth - width - 50)/2;
  var left = (screen.availHeight - height)/2;
  WinStat = window.open(url, "_blank", "top="+top+",left="+left+",width="+width+",height="+height+",toolbar=no,location=no,directories=no,status=no,menubar=no,resizable=yes,scrollbars=yes");
  return (typeof(WinStat) == 'object')?true:false;
}