header{
    width: 100%;
    height: 45px;
    border-bottom: 1px solid #ced4da;
    margin-bottom: 30px;
}
header nav{
    width: 1000px;
    height: 100%;
    margin: 0 auto;
}
section article{
    width: 1000px;
    margin: 0 auto;
    border-bottom: 1px solid #ced4da;
    margin-bottom: 30px;
}
section article ul li{
    list-style: none;
}