body {
    background-color: #f5f5f5;
    font-family: Arial, Helvetica, sans-serif;
    margin: 20px;
}

h1 {
    color: darkred;
    font-size: 32px;
    margin-bottom: 10px;
}

h2 {
    color: darkgreen;
    margin-top: 30px;
}

h3 {
    color: #333;
}

p {
    font-size: 18px;
    color: #333;
    line-height: 1.6;
    margin-top: 10px;
}

nav a {
    color: darkblue;
    text-decoration: none;
    margin-right: 10px;
}

nav a:hover {
    text-decoration: underline;
}

ul {
    background-color: #ffffff;
    padding: 15px;
    margin: 10px 0;
    border-radius: 5px;
}

ul li {
    margin-bottom: 5px;
}

table {
    background-color: #ffffff;
    border-collapse: collapse;
    margin-top: 10px;
    border: 1px solid #000;   /* Added to replace border="1" */
}

table th, table td {
    border: 1px solid #000;   /* Added to replace border="1" */
    padding: 8px;
}

img {
    display: block;
    margin: 20px 0;
    max-width: 400px;
    height: auto;
}

.tip {
    background-color: #e8f3ff;
    border-left: 4px solid #1e88e5;
    padding: 12px 16px;
    margin-top: 25px;
    font-style: italic;
    border-radius: 4px;
}