<html>
<body>
  <div class="parent">
    <div class="child"></div>
  </div>
    
</body>
</html>
* {
    margin: 0;
    padding: 0;
}

.parent {
  height: 100vh;
  width: 100%;
  background: #ebe834;
  
/* Centering div using CSS grid   */
  display: grid;
  align-items: center;
  place-items: center; /* shorthand property for  align-items and justify-items */
}

.child {
  height: 70px;
  width: 70px;
  background: #fe994a;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.