<script src="http://code.jquery.com/jquery-latest.js"></script>
<html>
<body style="height:100%;padding:34px;">
<div style="position:relative; height:200px;">
<div class="div" style="border:1px solid red;display:none; position:absolute; width:200px; height:200px;bottom:0;margin:auto 0 0 0">Текст</div></div>
<script>
$('.div').slideDown('slow');
</script>
</body>
</html>
display:none; position:relative; height:200px;