با جاوا اسکریپت میشه
<script>
window.setTimeout( "document.getElementById ('mydiv').style.display='none'" ,5000);
</script>
<div id="mydiv" style="position:absolute; width:200px; height:115px; z-index:9999; [COLOR=Red][B]left: 449px; top: 28px[/B][/COLOR]; background-color:#0000FF"></div>