function showHideHeadedList(){
  var listID = "prevweek";
	var Hnumber = "h3";
	var listtype = "ul";
  if(!document.getElementsByTagName) return false;
  if(!document.getElementById) return false;
	if(!document.getElementById(listID)) return false;
	var list = document.getElementById(listID);
	var listhead = list.getElementsByTagName(Hnumber);
	var lists = list.getElementsByTagName(listtype);
		// set a class of hide to all the lists and an onclick function to the headers
	for (var i=0; i<listhead.length; i++){
	  lists[i].className = "hide";
		listhead[i].onclick = function(){
		  var nextnode = node_after(this); // using mozilla node_after rather than nextSibling because of whitespace issue
			if(nextnode.className == "showblock"){
				nextnode.className = "hide";
			}
			else{
				nextnode.className = "showblock";
			}	
		}
	}
}
addLoadEvent(showHideHeadedList);