code: function getComputedStyle(prop, el) {
      var retVal = 0
      el = el || document.body // Not testable in phantonJS
  
      retVal = document.defaultView.getComputedStyle(el, null)
      retVal = null !== retVal ? retVal[prop] : 0
  
      return parseInt(retVal, base)
    }
docs: document.documentElement.offsetHeight is not reliable, so we have to jump through hoops to get a better value.