SOURCE

<div class="conatiner">
  Container
  <a class="btn">Blur</a>
</div>

.container, .btn{
  margin: 10px;
  height: 100px;
  line-height: 100px;
  width: 100px;
  background: #ff0000;
  color: #fff;
  font-size: 15px;
  text-align: center;
  /* position: relative; */

}
.conatiner {
  height: 400px;
  line-height: 400px;
  width: 400px;
  background: #ccc;
}
.btn {
  display: inline-block;
  position: absolute;
  z-index: 1;
  animation:mymove 3s infinite ease-out;
  -webkit-animation:mymove 3s infinite ease-out;
}
@keyframes mymove
{
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0.3;
  }
  100% {
    opacity: 1;
  }
}

@-webkit-keyframes mymove
{
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0.3;
  }
  100% {
    opacity: 1;
  }
}
/* 
@keyframes mymove
{
  0% {
    z-index: -1;
  }
  100% {
    z-index: 1;
  }
}

@-webkit-keyframes mymove
{
  0% {
    z-index: -1;
  }
  100% {
    z-index: 1;
  }
} */