Background-clip

div#box1 {
   color: #eee;
   border: 5px green;
   border-style: dotted double;
   background: blue;
   background-clip: padding-box; 
   }
   
   div#box2 {
   color: #eee;
   margin-top: 20px;
   border: 5px green;
   border-style: dotted double;
   background: blue;

This is box 1. Since I have background-clip: padding-box, the blue background won't go behind my border.

This is box 2. I don't have background-clip, so the blue background does go behind my border.