Код:
<script language="JavaScript">
<!--
function display_title() {
date = new Date();
var hours = date.getHours();
if (hours >= 6) { time_of_day = 'Доброе утро';}
if ((hours >= 12) && (hours < 18)) { time_of_day = 'Добрый день';}
if (hours >= 18) { time_of_day = 'Добрый вечер';}
if ((hours >= 0) && (hours < 6)){ time_of_day = 'Доброй ночи';}
document.write(time_of_day + '!');
}
//-->
</script>
<script language="JavaScript">
<!--
display_title();
//-->
</script>