body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
}
header {
    background: #35424a;
    color: #ffffff;
    padding: 20px;
    text-align: center;
}
nav ul {
    list-style: none;
    padding: 0;
}
nav ul li {
    display: inline;
    margin: 0 15px;
}