body {
    margin-left: auto;
    margin-right: auto;
    padding: 0;
}

header {
    box-sizing: border-box;
    width: 800px;
    height: 80px;
    margin-left: auto;
    margin-right: auto;
    padding: 10px;
    text-align: center;
    background-color: silver;
}

nav {
    width: 800px;
    margin-left: auto;
    margin-right: auto;
    background-color: silver;
}
/*
nav li ul {
    display: none;
    position: absolute;
    padding: 0;
    margin: 0;
    background-color: #1d91b9;
}
*/
nav li {
    display: inline;
}

nav li a {
    background-color: darkgrey;
}
/*
nav a {
    display: inline-block;
    padding: 10px;
    margin-left: 5px;
    background-color: green;
}

nav a:hover {
    background-color: silver;
    color: #1d91b9;
}

nav ul li:hover ul {
    display: block;
}

nav ul li:hover ul li {
    display: inherit;
}
*/
#sousmenu {
    display: none;
    position: absolute;
    padding: 0;
    margin: 0;
    background-color: transparent;
}

#sousmenu li {
    display: inherit;
}

.affichemenu {
    background-color: yellow;
}

.classtest {
    color: blue;
}

.rouge {
    color: red;
}

section {
    box-sizing: border-box;
    width: 800px;
    margin-left: auto;
    margin-right: auto;
    background-color: silver;
    line-height: 1.5em;
    font-size: 0.9em;
    padding: 15px 30px;
}

footer {
    width: 800px;
    text-align: center;
    color: yellow;
    margin-left: auto;
    margin-right: auto;
    background-color: grey;
}

a {
    text-decoration: none;
    color: green;
}

/*nav ul{
    color: blue;
    overflow: hidden;
    padding: 10px;
    margin:0;
    text-align: center;
}

li{
    display: inline-block;
}

nav ul li{
    padding: 10px;
}

nav ul li:hover{
    background-color: yellow;
}

.menu_deroulant{
    width: 100%;
    background-color: red;
    padding: 10px;
    text-align: left;
    box-sizing: border-box;
    cursor: pointer;
    display: none;
}
*/
@media screen and (max-width:700px){    
    nav ul{
        /* max-height: 0; */
    }
    .voir_menu{
        max-height: 20em;
    }
    .menu_deroulant {
        display: block;
    }    }
    nav ul li{
        box-sizing: border-box;
        padding: 10px;
        width: 100%;
        text-align: left;  
    }
}