html, body, .centered-container {
  height: 100%;
}

.centered-container {
  display: -webkit-flexbox;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-align: center;
  -ms-flex-align: center;
  -webkit-align-items: center;
  align-items: center;
  justify-content: center;
}