<section>
  <h2>Позиционируемый блок</h2>
  <p>без указания конкретных габаритов</p>
</section>
section {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background-color: hsl(168, 34%, 59%);
  padding: 20px;
  text-align: center; /*текст по центру*/
}

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