SOURCE

<div>
  Rabbit
</div>

div {
  text-align: center;
  line-height: 200px;
  font-size: 40px;
  color: #cffdf8;
  width: 200px;
  height: 200px;
  position: relative;
  background: #216583;
  border-radius: 20px;
	
	/* 重点是这句，IE13才开始支持 */
  filter: drop-shadow(2px 2px 10px rgba(0, 0, 0, .6));
}

div:after {
  content: '';
  display: block;
  width: 30px;
  height: 30px;
  background: #216583;
  position: absolute;
  z-index: -999;
  right: -15px;
  top: 20%;
  transform: rotate(45deg);
}