<html>
<head>
<style>
#a { position: relative; height: 150px; width: 100px; border: 2px solid black; }
#b { position: absolute; top: 25px; height: auto; bottom: 25px; }
</style>
</head>
<body>
<p>The blue box should be vertically centered in the black box with 25px of white on the top and bottom.</p>
<div id="a">
<img id="b" src="resources/square-blue-100x100.png">
</div>
</body>
</html>