@KeyFrames Opact

@keyframes name-of-animation {
  0%    { opacity: 0; }
  20%   { opacity: 1; }
  80%   { opacity: 0; }
  100%  { opacity: 1; }
}

.animate-this-element {
  animation: name-of-animation 5s infinite;
}
Awful Aardvark