template3-grid

<!DOCTYPE html>
<html>
<head>
  <title>With css grid</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <link href="https://cdnjs.cloudflare.com/ajax/libs/normalize/7.0.0/normalize.min.css" rel="stylesheet">
  <style type="text/css">
    html {
      height: 100%;
    }
    body {
      height: 100%;
      margin: 0 auto;
    }
    body {
      display: grid;
      grid-template-columns: 25% 75%;
      grid-template-rows: 100px auto 150px;
	 /* grid-gap: 1em;*/
    }
    header, footer {
      grid-column: 1 / 3;
    }
    header {
      background: #4eb543;
      z-index: 2;
      position: sticky;
      top: 0;
    }
    aside {
      background: #ee3643;
      overflow: auto;
    }
    main {
      background: #eaeaea;
      overflow: auto;
      padding: 20px;
    }
    footer {
      background: #32425c;
    }
  </style>
</head>
<body>
  <header>
    Header
  </header>
  <aside>
    Sidebar
  </aside>
  <main>
    Main
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
    <p>Some text some text some text some text.</p>
  </main>
  <footer>
    Footer
  </footer>
</body>
</html>