// JavaScript Document
function showOverlay() {
  var body = document.getElementsByTagName('body')[0]
  var overlay = document.getElementById('overlay')
  overlay.style.height=body.offsetHeight+"px"
  overlay.style.width=body.offsetWidth+"px"
  overlay.style.visibility="visible"
}

function closeOverlay() {
  var body = document.getElementsByTagName('body')[0]
  var overlay = document.getElementById('overlay')
  overlay.style.height=body.offsetHeight+"px"
  overlay.style.width=body.offsetWidth+"px"
  overlay.style.visibility="hidden"
}