body {
    font: normal 1em sans-serif;
    margin: auto;
    width: 60%;
}

footer {
    color: lightgray;
    text-align: center;
}

header {
    text-align: center;
}
nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid #e7e7e7;
    background-color: #f3f3f3;
}
nav li {
    float: left;
}
nav li a {
    display: block;
    color: #666;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}
nav li a:hover:not(.active) {
    background-color: #ddd;
}
nav li a.active {
    color: white;
    background-color: darkgray;
}