<div class="wrapper">
  <header></header>
  <main>
    <button>Кнопка</button>
    <div class="block"></div>
  </main>
  <footer></footer>
 </div>
header {
  height: 100px;
  background: #000;
}

.wrapper {
  height: 600px;
  overflow: auto;
}

.block {
  height: 800px;
  background: gray;
}

footer {
  height: 100px;
  background: #000;
}

External CSS

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External JavaScript

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