body {
  font-family: Arial, sans-serif;
  background: #f5f5f5;
  margin: 0;
  padding: 0;
}
header, footer {
  background: #333;
  color: white;
  padding: 1em;
  text-align: center;
}
nav a {
  margin: 0 15px;
  color: white;
  text-decoration: none;
}
nav a:hover {
  text-decoration: underline;
}
main {
  padding: 20px;
  max-width: 800px;
  margin: auto;
  background: white;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}