<div class="container">
  <div class="header">
    header
  </div>
   <div class="main">
     main
  </div>
</div>
.container {
  margin-top: 50px;
  width: 100px;
  height: 200px;
  display: flex;
  flex-direction: column;
  text-align: center;
}

.header {
  height: 40px;
  background: red;
}

.main {
  flex: 1;
  background: skyblue;
}

External CSS

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External JavaScript

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