body {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  min-height: 100vh;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
  -webkit-flex-direction: column;
      -ms-flex-direction: column;
          flex-direction: column;
}

main {
  -webkit-box-flex: 1;
  -webkit-flex: 1 0 auto;
      -ms-flex: 1 0 auto;
          flex: 1 0 auto;
}