```css
body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  color: #111;
  background-color: #ffffff;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 1.5rem;
}

header {
  border-bottom: 1px solid #ddd;
}

header h1 {
  margin: 0;
  font-size: 1.5rem;
}

nav {
  margin-top: 0.5rem;
}

nav a {
  margin-right: 1rem;
  text-decoration: none;
  color: #111;
  font-size: 0.9rem;
}

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

main h2 {
  margin-top: 0;
}

main h3 {
  margin-top: 1.5rem;
}

footer {
  border-top: 1px solid #ddd;
  margin-top: 3rem;
  font-size: 0.85rem;
  color: #444;
}
```