function addEvent(elm, evType, fn, useCapture){
  if (elm.addEventListener) 
  {
    elm.addEventListener(evType, fn, useCapture);
    return true;
  } else if (elm.attachEvent) { 
    var r = elm.attachEvent('on' + evType, fn);
    return r;
  } else {
    elm['on' + evType] = fn;
  }
}
addEvent(window, 'load', init, false)

function init()
{
   var el = document.getElementsByTagName('body');
   el[0].className = "js-enabled";
   
   var el = document.getElementById('linkNature');
   el.className = "nav_active";
   addEvent(el, 'click', doLinkNature, false);
   var el = document.getElementById('Naturediv');
   el.className = "active";
   
   var el = document.getElementById('linkOrigins');
   el.className = "nav_notactive";
   addEvent(el, 'click', doLinkOrigins, false);
   var el = document.getElementById('Originsdiv');
   el.className = "notactive";
   
   var el = document.getElementById('linkReading');
   el.className = "nav_notactive";
   addEvent(el, 'click', doLinkReading, false);
   var el = document.getElementById('Readingdiv');
   el.className = "notactive";
}

function doLinkNature()
{
   var el = document.getElementById('linkNature');
   el.className = "nav_active";
   var el = document.getElementById('Naturediv');
   el.className = "active";
   var el = document.getElementById('linkOrigins');
   el.className = "nav_notactive";
   var el = document.getElementById('Originsdiv');
   el.className = "notactive";
   var el = document.getElementById('linkReading');
   el.className = "nav_notactive";
   var el = document.getElementById('Readingdiv');
   el.className = "notactive";
   
}

function doLinkOrigins()
{
   var el = document.getElementById('linkNature');
   el.className = "nav_notactive";
   var el = document.getElementById('Naturediv');
   el.className = "notactive";
   var el = document.getElementById('linkOrigins');
   el.className = "nav_active";
   var el = document.getElementById('Originsdiv');
   el.className = "active";
   var el = document.getElementById('linkReading');
   el.className = "nav_notactive";
   var el = document.getElementById('Readingdiv');
   el.className = "notactive";
}

function doLinkReading()
{
   var el = document.getElementById('linkNature');
   el.className = "nav_notactive";
   var el = document.getElementById('Naturediv');
   el.className = "notactive";
   var el = document.getElementById('linkOrigins');
   el.className = "nav_notactive";
   var el = document.getElementById('Originsdiv');
   el.className = "notactive";
   var el = document.getElementById('linkReading');
   el.className = "nav_active";
   var el = document.getElementById('Readingdiv');
   el.className = "active";
}