<div id="DIV1" style="border: solid 1px red;">
<div style="position: relative; top: 50%;">This text with top percent relative and containing block auto should appear inside the red border</div>
</div>
<div id="DIV2" style="border: solid 1px red;">
<div style="position: relative; bottom: 50%;">This text with bottom percent relative and containing block auto should appear inside the red border</div>
</div>