<body>
  <div class="content">
    <header>
    ヘッダ
    </header>
    <main>
      コンテンツ
    </main>
  </div>
  <footer>
    フッタ
  </footer>
</body>
body {
  margin: 0;
  padding: 0;
  position: relative;
}
header {
  width: 100%;
  background: #ccdd33;
}
.content {
  min-height: calc(100vh - 50px);
}
footer {
  width: 100%;
  height: 50px;
  background: #44aa33;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.