Je teste

<!DOCTYPE html>
<html lang="fr">
<head>
  <meta charset="UTF-8">
  <title>Mise en page en colonnes</title>
  <style>
    #entete {
      padding: 20px;
      background-color: #ccf;
      text-align: center;
    }
    #conteneur {
      display: table;
    }
    #gauche {
      display: table-cell;
      width: 20vw;
      padding: 20px;
      background-color: #fcc;
    }
    #centre {
      display: table-cell;
      width: 60vw;
      padding: 20px;
      background-color: #fff;
    }
    #droite {
      display: table-cell;
      width: 20vw;
      padding: 20px;
      background-color: #ffc;
    }
    #pieddepage {
      padding: 20px;
      background-color: #cff;
      text-align: center;
    }
  </style>
</head>
<body>
  <div id="entete">
    En-tête
  </div>
  
  <div id="conteneur">
      
    <div id="gauche">
      Barre latérale gauche
    </div>
    <div id="centre">
      Contenu
    </div>
    <div id="droite">
      Barre latérale droite
    </div>
    
  </div>
  
  <div id="pieddepage">
    Pied de page
  </div>
</body>
</html>