<div class="contentBox">
  <span class="contentBox__item">item</span>
</div>
.contentBox {
  display: flex;
  height: 200px;
  background: #ddd;
}
.contentBox__item {
  margin: auto;
  width: 80px;
  height: 50px;
  background: blue;
  color: #fff;
}

External CSS

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External JavaScript

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