Paste code

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
 div {height: 30px;border:1px #000;}
 p   {height: 50%;border:1px #000;}
</style>
</head>

<body>
 <div >
   <p >Half as tall</p>
 </div>
</body>
</html>