/* Element selector */
body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
}

/* ID selector */
#main-title {
    color: darkblue;
    text-align: center;
}

/* Class selector */
.section-header {
    color: darkgreen;
    margin-top: 20px;
}

/* Extra styling */
img {
    display: block;
    margin: 10px auto;
}