function setCenter() {
  var height = document.documentElement.clientHeight;
  var myValue = parseInt((height - 400)/2) - 40;
  if (myValue > 0)
    document.getElementById("mypage").style.marginTop = myValue + "px";
}
function setHeight(minheight) {
  var height = document.documentElement.clientHeight;
  var mainHeight = height - 115;
  
  if (mainHeight > minheight) {
    document.getElementById('page').style.height = mainHeight + 'px';
  } else {
    document.getElementById('page').style.height = minheight + 'px';
  }
}