body {
    font-family: 'Arial', sans-serif;
    background-color: #f8f9fa;
    margin: 0;
    padding: 0;
}

#container {
    display: flex;
    flex-direction: column;
    max-width: 900px;
    margin: 50px auto;
    border: 1px solid #ced4da;
    border-radius: 8px;
    background-color: #ffffff;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

header {
    background-color: #007bff;
    color: white;
    padding: 20px;
    text-align: center;
}

main {
    padding: 20px;
}

aside {
    background-color: #e9ecef;
    padding: 15px;
    margin: 20px 0;
}

aside h2 {
    margin-top: 0;
}

footer {
    background-color: #343a40;
    color: white;
    text-align: center;
    padding: 10px;
}