function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}



function showSection(id) {
	var divs = document.getElementsByTagName("div");
	for (var i=0; i<divs.length; i++) {
		if (divs[i].className.indexOf("section") == -1) continue;
		if (divs[i].getAttribute("id") != id) {
			divs[i].style.display = "none";
			} else {
			divs[i].style.display = "block";		
		}
	}
}

function prepareInternalnav () {
	if (!document.getElementsByTagName) return false;
	if (!document.getElementById) return false;
	if (!document.getElementById("internalnav")) return false;
	var nav = document.getElementById("internalnav");
	var links = nav.getElementsByTagName("a");
	for (var i=0; i<links.length; i++) {
		var sectionId = links[i].getAttribute("href").split("#")[1];
		if (!document.getElementById(sectionId)) continue;
		document.getElementById(sectionId).style.display = "none";
		links[i].destination = sectionId;
		links[i].onclick = function() {
			showSection(this.destination);
			return false;
		}
	}
}
addLoadEvent(prepareInternalnav);