.menu {
    list-style: none;
    display: flex;
    gap: 30px;
    background: cyan;
    padding: 10px;
}

.menu > li {
    position: relative;
}

.menu a {
    text-decoration: none;
    color: black;
    padding: 8px 12px;
    display: block;
}

.submenu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    list-style: none;
    background: lightblue;
    padding: 0;
    min-width: 200px;
}

.submenu li a {
    padding: 8px;
}

.menu li:hover .submenu {
    display: block;
}

.contenu {
    margin-left: 260px;
    padding: 20px;
}