ASPECT RATIO 16:4

Run
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>HTML</title>
<style>
   .container {
      padding-top: 56.25%; /* 16:9*/
	  background-color: #ccc;
	  position: relative;
	  width: 100%;
   }
     
</style>
</head>
<body>
   <h2> Maintaining aspect ratio of div element </h2>
   <div class="container">
	</div>
</body>
</html>