function sayhello()
{
  var word;
  
  if (!document.layers&&!document.all)
     return
  var Digital=new Date()
  var hours=Digital.getHours()

  if (hours<=6){
  	word="嗨! 还不睡!";
}
  if (hours>6 && hours<=8){
  	word="大家早上好";
}
  if (hours>8 && hours<=12){
  	word="同学们,上午好!";
}
  if (hours>12 && hours<=18){
  	word="同学们,下午好!";
}
  if (hours>18 && hours<=24){
  	word="同学们，晚上好！";
}

//word="<p align='right'>"+word+"</P>";
document.writeln(word);
}