<SCRIPT LANGUAGE="JavaScript">        
currentTime = new Date();        
if (currentTime.getHours() >= 6 && currentTime.getHours() <= 11 )        
document.write("Доброе утро, ");        
if (currentTime.getHours() >= 12 && currentTime.getHours() <= 17 )        
document.write("Добрый день, ");        
if (currentTime.getHours() >= 18 && currentTime.getHours() <= 23)        
document.write("Добрый вечер, ");        
if (currentTime.getHours() >= 0 && currentTime.getHours() <= 5)        
document.write("Доброй ночи, ");        
</SCRIPT>