body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
}
header, nav, footer {
    background-color: #333;
    color: white;
    padding: 10px 20px;
    text-align: center;
}
nav a {
    color: white;
    margin: 0 10px;
    text-decoration: none;
}
main {
    padding: 20px;
    background: white;
}
img {
    display: block;
    margin: 20px auto;
    max-width: 90%;
}
footer {
    margin-top: 20px;
}