<div class="parent">
  <p id="em">font-size: 1.5em;</p>
</div>
<div class="parent">
  <p id="px">font-size: 24px;</p>
</div>
.parent {
  font-size: 16px;
}

#em {
  font-size: 1.5em;
}

#px {
  font-size: 24px;
}

div {
  background-color: thistle;
  width: 300px;
  padding: 10px;
  margin: 10px;
}

html {
  font-family: arial;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.