@media screen and (max-width: 991px) {
    header {
        background: #1a283c;
    }
}

@media screen and (max-width: 767px) {
    body > .container-fluid {
        padding:0;
    }

    header {
        background: #1a283c;
    }
    header nav {
        text-align: center;
    }
    header nav a, header nav span {
        display: block;
        padding: 5px 0;
        text-align: center;
    }

    .formulaire-content {
        padding-left: 15px;
        padding-right: 15px;
    }
}

@media screen and (max-width: 520px) {
    .formulaire-content {
        padding-left: 15px;
        padding-right: 15px;
    }
}