<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>