function closeDiv() {
  document.getElementById('cover').style.display='none';
  document.getElementById('infobox').style.display='none';
  }

function getPageSize() {
  var xScroll, yScroll;

	if (window.innerHeight && window.scrollMaxY) {	
		xScroll = window.innerWidth + window.scrollMaxX;
		yScroll = window.innerHeight + window.scrollMaxY;
	} else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
		xScroll = document.body.scrollWidth;
		yScroll = document.body.scrollHeight;
	} else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari
		xScroll = document.body.offsetWidth;
		yScroll = document.body.offsetHeight;
	}

	var windowWidth, windowHeight;
	if (self.innerHeight) {	// all except Explorer
		if(document.documentElement.clientWidth){
			windowWidth = document.documentElement.clientWidth; 
		} else {
			windowWidth = self.innerWidth;
		}
		windowHeight = self.innerHeight;
	} else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
		windowWidth = document.documentElement.clientWidth;
		windowHeight = document.documentElement.clientHeight;
	} else if (document.body) { // other Explorers
		windowWidth = document.body.clientWidth;
		windowHeight = document.body.clientHeight;
	}	
	var pageHeight,pageWidth;
	// for small pages with total height less then height of the viewport
	if(yScroll < windowHeight){
		pageHeight = windowHeight;
	} else { 
		pageHeight = yScroll;
	}
		// for small pages with total width less then width of the viewport
	if(xScroll < windowWidth){	
		pageWidth = xScroll;		
	} else {
		pageWidth = windowWidth;
	}

  return Array(pageWidth,pageHeight,windowHeight);
  }
  
var infobox_w = 500;
var infobox_h = 300;

function createDiv() {

  var size = getPageSize();
  
  var cover = document.getElementById('cover');
  var infobox = document.getElementById('infobox');
  
  cover.style.display="";
  cover.style.width = size[0]+"px";
  cover.style.height = size[1]+"px";
  
  infobox.style.display=""; 
  infobox.style.marginLeft = Math.ceil((size[0]-infobox_w)/2)+"px";
  infobox.style.marginTop = Math.ceil((size[2]-infobox_h)*0.3)+"px";
  
  }