window.onload = function(){
  var wrapper = document.getElementById('ContainerMain');
  var footer = document.getElementById('Footer');
  var showHeight = getshowHeight();
  var bodyHeight = document.body.scrollHeight;
  if(showHeight>=bodyHeight){
    wrapper.style.height = showHeight + 'px';
    //footer.style.position = "absolute";
    footer.style.bottom = "0px";
  }
}

function getshowHeight() {
  if(window.innerHeight)
    return window.innerHeight;
  if(document.body.parentNode.clientHeight)
    return document.body.parentNode.clientHeight;
  if(document.body.clientHeight)
    return document.body.clientHeight;
}