var doc;

function doc_height() {
  var header = document.getElementById('HeaderBox').offsetHeight;
  var menu = document.getElementById('MainMenuBox').offsetHeight;
  var content = document.getElementById('ContentBox').offsetHeight;
  var footer = document.getElementById('FooterBox').offsetHeight;

  doc = header + menu + 2 + content + 2 + footer + 8;
  
  doc = doc + "px";

  document.getElementById('doc').style.height = doc;
}