Exercicio CSS

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Exercício</title>
  <link rel="stylesheet" href="css/exercicio.css">
</head>

<body>

  <div class="container">
    <section>
      <aside class="esquerda"></aside>
      <aside class="direita"></aside>
    </section>
  </div>

</body>

</html>