body {
  margin: auto;
  width: 50%;
  border: 1px solid black;
  padding: 10px;
  font-family: Arial, Helvetica, sans-serif;
  font-size:24px;
  text-align: center;
}

#entete {
width:100%;
height:100px;
background-color: white;
display: flex;
align-items: center;
justify-content: center;
text-align: justify;
}
#main {
margin-left: 30px;
margin-right: 30px;
overflow: hidden;
}
#menu {
float:left;
width:240px;
height:400px;
background-color:#FF3366;
  margin:20px;
display: flex;
align-items: center;
justify-content: center;

}

#contenu {
float:right;
width:40%;
height:400px;
background-color: mediumpurple;
margin-left: 280px;
margin:20px;
display: flex;
align-items: center;
justify-content: center;

}

#footer {
width:100%;
height:100px;
background-color: green;
display: flex;
align-items: center;
justify-content: center;
}