code HTML
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="description" content="">
<meta name="author" content="">
<meta name="generator" content="">
<title>Accueil</title>
<link rel="canonical" href="https://getbootstrap.com/docs/5.1/examples/features/">
<!-- Bootstrap core CSS -->
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-1BmE4kWBq78iYhFldvKuhfTAU6auU8tT94WrHftjDbrCEXSU1oBoqyl2QvZ6jIW3" crossorigin="anonymous">
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<meta name="theme-color" content="#7952b3">
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</head>
<body>
<div class="container" id="header">
<div class="row">
<div class="col-md-4">
<h1 class="h6">Révision / Cours de développement web</h1>
</div>
<div class="col-md-4"><nav class="navbar navbar-expand-lg navbar-light bg-light text-center" id="menu-header"><div class="container-fluid"><div class="collapse navbar-collapse"></div></div></nav></div>
<div class="col-md-4">
</div>
</div>
</div>
<div class="container" id="center">
<div class="row">
Salut
</div>
</div>
<div class="container" id="footer">
<div class="row">
<div class="col-md-4"></div>
<div class="col-md-4">
<nav class="navbar navbar-expand-lg navbar-light bg-light text-center" id="menu-footer"><div class="container-fluid"><div class="collapse navbar-collapse"></div></div></nav>
</div>
<div class="col-md-4"></div>
</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.10.2/dist/umd/popper.min.js" integrity="sha384-7+zCNj/IqJ95wo16oMtfsKbZ9ccEh31eOz1HGyDuCQ6wgnyJNSYdrPa03rtR1zdB" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.min.js" integrity="sha384-QJHtvGhmr9XOIpI6YVutG+2QOK9T+ZnN4kzFN1RtK3zEFEIsxhlmWl5/YESvpZ13" crossorigin="anonymous"></script>
<script>
</script>
</body>
</html>