<html>
<head>
<script type="text/javascript" >
function hideDiv(){
document.getElementById('myDiv').style.display='none';
}
</script>
</head>
<body onload="setTimeout('hideDiv()', 5000)">
<div id="myDiv" style="background-color:blue;position:absolute;left:200;top:300;width:300px;height:200px;" >my text... </div>
</body>
</html>