function toggleNav(id,link) {
    // check to see if the link is an HTML element
    if (link.nodeType != 1) {
        // it isn't, change it to its previous sibling
        link = link.previousSibling;
    }
	var list = document.getElementById(id);
	// check status of the ul
	if (link.innerHTML == "+") {
		// <ul> needs to be expanded (shown)
		link.innerHTML = "-";
		// show all child <li>
		items = list.childNodes;
		for(i=0;i<items.length;++i) {
            if (items[i].nodeType == 1) {
                items[i].style.display = "inline";
			}
		}
	} else {
		// <ul> needs to be contracted (hidden)
		link.innerHTML = "+";
		// hide all child <li>
		items = list.childNodes;
		for(i=0;i<items.length;++i) {
            if (items[i].nodeType == 1) {
                items[i].style.display = "none";
            }
		}
	}
}