<div class="container">
  <div class="hotspot pulse-dot">
      <div class="pulse-ring">
      </div>
  </div>
</div>

body{
  background: #333;
}
.container{
  position: absolute;
  width: 100%;
  height:  100%;
}

.hotspot {
  position: absolute;
  background: #FFF;
  background: rgba(255,255,255,0.75);
  width: 32px;
  height: 32px;
  border-radius: 50%;
  left: 50%;
  top: 50%;
  /*correct centered position...*/
  -webkit-transform: translateX(-16px) translateY(-50%);
  transform: translateX(-50%) translateY(-50%);

}
.pulse-dot{
  animation: pulse-dot infinite 3.5s;
}
.pulse-ring {
  content: '';
  width: 32px;
  height: 32px;
  border: 8px solid #FFF;
  border-radius: 50%;
  position: absolute;
  top: -8px;
  left: -8px;
  animation: pulse-ring infinite 3.5s;
}

/* Animations */
@-webkit-keyframes pulse-dot {
  0% {
    -webkit-transform: scale(1, 1);
  }
 
  30%{
    -webkit-transform: scale(1.25, 1.25);
  }
  
  100% {
    -webkit-transform: scale(1, 1);
  }
}
@keyframes pulse-dot {
  0% {
    transform: scale(1, 1);
  }
 
  30%{
    transform: scale(1.25, 1.25);
  }
  
  100% {
    transform: scale(1, 1);
  }
}

@-webkit-keyframes pulse-ring {
  0% {
    -webkit-transform: scale(1, 1);
    opacity: 0;
  }
 
  25%{
    opacity: .5;
  }
  
  100% {
    -webkit-transform: scale(1.8, 1.8);
    opacity: 0;
  }
}
@keyframes pulse-ring {
  0% {
    transform: scale(1, 1);
    opacity: 0;
  }
 
  25%{
    opacity: .5;
  }
  
  100% {
    transform: scale(1.8, 1.8);
    opacity: 0;
  }
}