body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

#header {
    background:  #333;
    color: #fff;
    padding: 20px 0;
    text-align: center;
}

#header h1 {
    margin: 0;
}

#leftNav {
    background: #f4f4f4;
    padding: 10px;
    width: 20%;
    float: left;
    height: 100vh;
    box-sizing: border-box;
}

#leftNav ul {
    list-style: none;
    padding: 0;
}

#leftNav ul li {
    margin: 10px 0;
}

#leftNav ul li a {
    text-decoration: none;
    color: #333;
    font-weight: bold;
}

#leftNav ul li a:hover {
    color: #007BFF;
}

#mainContent {
    float: left;
    width: 80%;
    padding: 20px;
    box-sizing: border-box;
}

#mainContent img {
    margin: 20px 0;
}

#footer {
    clear: both;
    background: #333;
    color: #fff;
    text-align: center;
    padding: 10px;
    margin-top: 20px;
}