/* Intentional mistakes included */
body {
    font-family: Arial, sans-sarif; /* typo: should be sans-serif */
    background-colour: #f5f5f5; /* invalid property: should be background-color */
    margin: 0;
    padding: 0;
}

header {
    background: #333;
    color: white;
    padding: 10px;
}

nav a {
    color: yellow;
    text-decoration: none;
    margin-right: 15px;
}

main {
    padding: 20px;
}