<section>
  <h2>Центрируемый блок</h2>
  <p>с извесными габаритами</p>
</section>
section {
  position: absolute;
  top: calc(50% - 70px); /*140px/2=70px*/
  left: calc(50% - 110px); /*220px/2=110px*/
  width: 220px;
  height: 140px;
  background-color: rgb(116, 186, 172);
  text-align: center;
}

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