body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background: #f5f5f5;
    color: #333;
}
header, footer {
    background: #004080;
    color: white;
    padding: 1em;
    text-align: center;
}
nav ul {
    list-style: none;
    padding: 0;
    display: flex;
    justify-content: center;
    background: #0066cc;
    margin: 0;
}
nav li {
    margin: 0 1em;
}
nav a {
    color: white;
    text-decoration: none;
}
main {
    padding: 2em;
    background: white;
    margin: 1em auto;
    max-width: 900px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
}