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);