function getWindowHeight() {
  var windowHeight = 0;
  if (typeof(window.innerHeight) == 'number') {
	  windowHeight = window.innerHeight;
} else {
	  if (document.documentElement && document.documentElement.clientHeight) {
		  windowHeight = document.documentElement.clientHeight;
} else {
		if (document.body && document.body.clientHeight) {
			windowHeight = document.body.clientHeight;
		}
	}
}
return windowHeight;
}
function setFooter() {
  if (document.getElementById) {
	  var windowHeight = getWindowHeight();
	  if (windowHeight > 0) {
		  var contentHeight = document.getElementById('page').offsetHeight;
		  var footerElement = document.getElementById('footer');
		  var footerHeight  = footerElement.offsetHeight;
		  if (windowHeight - (contentHeight + footerHeight) >= 0) {
			  footerElement.style.top = (windowHeight - (contentHeight + footerHeight)) + 'px';
		  } else {
			  footerElement.style.top = '0px';
		  }
	  }
  }
}
addLoadEvent(setFooter);
window.onresize = function() {
setFooter();
}