function greeting(){
   var today = new Date();
   var hour = today.getHours();

   document.write("Good ");
   if (hour < 12)
      document.write("morning. ");
   else if (hour <= 18)
      document.write("afternoon. ");
   else
      document.write("evening. ");
}

ver=parseInt(navigator.appVersion);

if (ver>=4) {
  greeting();
}