[class^="container-float"] {
  height: 100vh; /* Unit irrevelant */
}
[class^="container-float"]::after {
  content: "";
  display: table;
  clear: both;
}
[class^="centered-float"] {
  position: relative;
  float: left; /* Collapses box */
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}
[class^="container-noFixedHeight"] {
  position: relative;
  min-height: 100vh; /* Unit irrevelant */
}
[class^="centered-noFixedHeight"] {
  position: absolute; /* Collapses box */
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}
[class^="container-absolute"] {
  position: relative;
  height: 100vh; /* Unit irrevelant */
}
[class^="centered-absolute"] {
  position: absolute;
  max-width: 50%;
  max-height: 18.5rem;
  top: 0; left: 0; bottom: 0; right: 0;
  margin: auto;
}
.container-flexbox { /* Unsupported in IE9 */
  height: 100vh; /* Unit irrevelant */
  display: flex; /* Collapses box */
  align-items: center;
  justify-content: center;
}
.centered-flexbox {
}
Centre?

More options and variants: Absolute horizontal vertical centering CSS