body {
}

header, section, footer {
  display: block;
}

header {
  text-align: center;
  padding: 20px;
  background-color: #444444;
}

section {
  padding: 20px;
  background-color: #aaaaaa;
}

footer {
  background-color: #666666;
  padding: 20px;
  text-align: right;
}