Get your own website Result Size: 625 x 565
x
 
<!DOCTYPE html>
<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>