style.css

.alert{
  animation-name: alertMe;
  animation-duration: 1s;
  animation-delay: 0s;
  animation-iteration-count: infinite;
  animation-timing-function: ease-in-out;
  animation-fill-mode: forward;
  animation-direction: alternate;

  -webkit-animation-name: alertMe;
  -webkit-animation-duration: 1s;
  -webkit-animation-delay: 0s;
  -webkit-animation-iteration-count: infinite;
  -webkit-animation-timing-function: ease-in-out;
  -webkit-animation-fill-mode: forward;
  -webkit-animation-direction: alternate;

  -moz-animation-name: alertMe;
  -moz-animation-duration: 1s;
  -moz-animation-delay: 0s;
  -moz-animation-iteration-count: infinite;
  -moz-animation-timing-function: ease-in-out;
  -moz-animation-fill-mode: forward;
  -moz-animation-direction: alternate;
  position: relative;  
}

@keyframes alertMe {

  0% {
background-color: rgba(255, 0, 0, 1)
  }

  100% {
background-color: rgba(255, 0, 0, 0)
  }
}

@-webkit-keyframes alertMe {

  0% {
background-color: rgba(255, 0, 0, 1)
  }

  100% {
background-color: rgba(255, 0, 0, 0)
  }
}

@-moz-keyframes alertMe {

  0% {
background-color: rgba(255, 0, 0, 1)
  }

  100% {
background-color: rgba(255, 0, 0, 0)
  }
}