vertical-align: 300%
<!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' xml:lang='en'>
<head>
<title>vertical-align</title>
<style rel='stylesheet' type='text/css'>
p {
font: 12px sans-serif;
}
p#control {
font-size: 100px;
margin: 5px 0;
}
p#control span {
border: 1px solid rgb(200, 200, 200);
background: rgb(244, 244, 244);
}
p#control span span {
vertical-align: 300%;
font-size: 20px;
background: white;
border: 1px solid black;
}
</style>
</head>
<body>
<p>
this is a test.
</p>
<p id='control'>
<span>Nn Oo Pp <span>300%</span></span>
</p>
</body>
</html>