position: fixed;
  width: 100%;
  height: 25%;
  left: 0;
  top: 0;
  right: 0;
  bottom: auto;
  border: 1px solid gray;
 

  position: fixed;
  width: 25%;
  height: 75%;
  left: 0;
  top: 25%;
  right: auto;
  bottom: 0;
  background-color: lightcyan;
  border: 1px solid gray;
 

  position: fixed;
  width: auto;
  height: 75%;
  left: 25%;
  top: 25%;
  right: 0;
  bottom: 0;
  background-color: lightyellow;
  border: 1px solid gray;