CSS MAX-WIDTH

Run
<!DOCTYPE html>
<html>
<head>
<style>
div {
  height: 200px;
  max-width: 500px;
  background-color:#89eff5;
  text-align: center;
  font-size: 30px;
}
</style>
</head>
<body>
<div>Hello!</div>
</body>
</html>