.ribbon-contents {
  margin: 0;
  padding: 0;
  background: crimson;
  color:white;
  padding:1em 0;
  position: absolute;
  top:0;
  right:0;
  transform: translateX(30%) translateY(0%) rotate(45deg);
  transform-origin: top left;
  box-shadow: 0 5px 10px rgba(0,0,0,.1);
  text-shadow: 0 1px 1px rgba(0,0,0,.2);
  z-index: 1;
  font-weight: bold;
}
.ribbon-contents:before,
.ribbon-contents:after {
  content: '';
  position: absolute;
  top:0;
  margin: 0 -1px; /* tweak */
  width: 100%;
  height: 100%;
  background: crimson;
}
.ribbon-contents:before {
  right:100%;
}

.ribbon-contents:after {
  left:100%;
}