an example.. in your browser change the text-size or use CTRL and move your middle mouse wheel back and forth. Instead of the text being vertically centered, its moved up or down with the font size.
Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Untitled Document</title>
<link rel="stylesheet" type="text/css" media="screen" />
<style type="text/css">
#test {
height: 50px;
width: 200px;
text-align: center;
border: solid 1px;
font-size: 66%;
font-family: verdana, tahoma, sans-serif;
line-height: 50px;
}
</style>
<script type="text/javascript"></script>
</head>
<body>
<div id="test">Some text</div>
</body>
</html>
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