var ie = document.all;

function registerExpandCollapseEvents() {
	var els = document.getElementsByTagName("A");
	for (i in els) {
		el = els[i];
		if (el.id && el.id.indexOf("ch") == 0) {
                    if (el.addEventListener)
			el.addEventListener("click",toggleListDisplay,false);
                    else if (el.attachEvent)
                        el.attachEvent("onclick",toggleListDisplay);
                    else
                        alert("Failed to register event handler...");
		}
	}
}

function toggleListDisplay(evt) {
		
	// stop event propogation to parent elements
        //
	if (!evt) evt = window.event;
	evt.cancelBubble = true;
	if (evt.stopPropation) evt.stopPropogation();
	
	// find first child element of <li> that is a new list <ul>
	// and toggle its display style between block and none	
        // NOTE that clicking the category name will cause event to
        // report the <STRONG> and not the <LI> so adjust for that
        //
        var el = (ie ? evt['srcElement'] : evt['target']);
        while (el.nodeName != "LI") el = el.parentNode;
        
	var children = el.childNodes;
	for(index in children) {
		var child = children[index];
		if (child.nodeName == "UL") {
			toggleDisplay(child);
			break;
		}
	}
		
}

function toggleDisplay(elm) {
	if (elm.style.display == "none") elm.style.display = "block";
	else elm.style.display = "none";
}