css flash

http://double-d.cc/

    -webkit-animation-name: flash;
    animation-name: flash;
    -webkit-animation-duration: 1s;
    animation-duration: 1s;
    -webkit-animation-iteration-count: infinite;
    animation-iteration-count: infinite;

@-webkit-keyframes flash {
  0%, 100% {
    opacity: 1;
  }

  50% {
    opacity: 0;
  }
}

@keyframes flash {
  0%, 100% {
    opacity: 1;
  }

  50% {
    opacity: 0;
  }
}

.flash {
  -webkit-animation-name: flash;
  animation-name: flash;
}