<html>
<head>
<style>
#parent {
height: 100px;
width: 250px;
border: 2px solid blue;
}
#child {
height: 50%;
width: 75%;
border: 2px solid red;
}
</style>
</head>
<body>
<h1>The height Property</h1>
<div id="parent">
<div id="child">I'm half the height of my parent.</div>
</div>
</body>
</html>