Использование ::after и ;;before

gistfile1.txt

<div class="new">Див</div>


.new {
  width:200px;
  height:20px;
  border:1px solid black;
  padding:5px;
  position: relative; 
}
.new::before {
  content: "";
  height:30px;
  width:40px;
  border:1px solid green;
  background-color:green;
  position:absolute;
  right:-1px;
  top:-1px;
  
}