05-values-and-units/using-em-for-margins-and-sizing.html

<!DOCTYPE html>
<html>
<head>
<title>Using em for margins and font sizing</title>
<style type="text/css">
h1 {font-size: 24px;}
h2 {font-size: 18px;}
p {font-size: 12px;}
h1, h2, p {margin-left: 1em;}
small {font-size: 0.8em;}
</style>
</head>
<body>

<h1>Left margin = <small>24 pixels</small></h1>
<h2>Left margin = <small>18 pixels</small></h1>
<p>Left margin = <small>12 pixels</small></p>

</body>
</html>