<head>
 <style>
div{
border: 2px solid black;
   } 
.box {
margin: 20px;
    }
 </style>
</head>
<body>
<div>div with no margin</div>
<div class="box">Content with 20px margin on all sides</div>
<div>div with no margin</div>
</body>

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.