html {
  height: 100%;
}

body {
  min-height: 100%;
  display: flex;
  flex-direction: column;
  margin: 0;
}

header,
#header {
  flex-shrink: 0;
}

main,
.main,
#contents {
  flex: 1 0 auto;
}

footer,
.footer,
#footer {
  flex-shrink: 0;
  margin-top: auto;
}