body {
  background: #222;
}
div {
  width: 200px;
  height: 240px;
  line-height: 60px;
  background: #eee;
  text-align: center;
  font-size: 480px;
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  margin: auto;
  overflow: hidden;
}
div:before {
  content: "---";
  display: block;
}
div:after {
  content: "";
  display: block;
  position: absolute;
  top: 0; right: 0;
  width: 0;
  height: 0;
  border: solid 80px transparent;
  border-left: none;
  border-top: none;  
  border-bottom: solid 80px #ccc; 
  background: #222;
}