<header>
  <h1>Brand</h1>
  <nav>
    <span>Menu1</span>
    <span>Menu2</span>
    <span>Menu3</span>
  </nav>
</header>

<main>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
  <p>This is the main area.</p>
</main>   
header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  
  height: 75px;
  padding: 1rem;
  color: white;
  background: teal;
  font-weight: bold;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

h1, p {
  margin: 0;
}

main {
  padding: 1rem;
  height: 100%;  
}

body {
  background: #EEE;
}

body, html {
  height: 200%;
}

* {
  box-sizing: border-box;
}

External CSS

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External JavaScript

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