.conteneur{
    width: 900px;
    margin: 0 auto;
    background: fuchsia;
}

header{
    background: tomato;
    height: 80px;
}

nav{
    background: yellow;
    color: black;
    height: 30px;
}

.gauche, .droite{
    background: gray;
    color: black;
    display: flex;
    flex-direction: column;

}

.c, .d{
    text-align: right;
}

.a{
    background: green;
    height: 200px;
    width: 200px;
    
}

.b{
    background: red;
    height: 200px;
    width: 200px;
}

.c{
    background: rgb(216, 216, 209);
    color: black;
    height: 200px;
    width: 200px;
}

.d{
    background: purple;
    color: white;
    height: 200px;
    width: 200px;
}

.droite{
    margin-left: 800px;
    margin-top: -815px;
    position: absolute;
    right: 233px;
    
}

.milieu{
    background: blue;
    color: white;
    height: 400px;
    width: 500px;
    margin-left: 200px;
    position: relative;
    bottom: 415px;
    
}

.bas{
    height: 70px;
    background: goldenrod;
    color: black;
    margin-top: -432px;
}