body {
  font-family: sans-serif;
  margin: 0;
  background: #f4f4f4;
  color: #333;
}
header {
  background: #4caf50;
  color: white;
  padding: 1em;
  text-align: center;
}
nav a {
  margin: 0 1em;
  color: white;
  text-decoration: none;
}
main {
  padding: 2em;
  max-width: 800px;
  margin: auto;
  background: white;
}
footer {
  text-align: center;
  padding: 1em;
  background: #ddd;
  margin-top: 2em;
}
table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1em;
}
th, td {
  border: 1px solid #aaa;
  padding: 0.5em;
  text-align: left;
}