<div></div>
div {
  background-color: red;
  border-radius: 50%;
  height: 250px;
  width: 250px;
  margin: 50px;
  animation: pulsirovaniye 2s ease infinite;
}

@keyframes pulsirovaniye {
  0% {
    transform: scale(1);
  }

  50% {
    transform: scale(1.3);
  }

  100% {
    transform: scale(1);
  }
}

External CSS

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External JavaScript

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