var max_depth = 3;
            var cur_menu = new Array(max_depth + 1);
            // keep track of current menus
            // index 0 = menubar img (0..6) of current page
            // index 1 = menubar img (0..6) of current mouseover
            // index 2,3 = nav id of current mouseover for level 2,3
            
            function showMenu(level,id) {
            	if (!isDOMcompliant()) { return; }
            	var submenu = document.getElementById("nav" + level + "_" + id);
            	hideMenu(level); 
                cur_menu[level] = id;
                if (level == 1) {
                    menu1swapImg(id,true);
                    showMenu(2,id);
                    return;
                } else if (level > 1) {
                    submenu.style.visibility = "visible";
                    submenu.style.display = "inline";
                }
            }
            
            function hideMenu(level) {
            	if (!isDOMcompliant()) { return; }
            	
            	// hide all deeper menus
            	if (level < max_depth) { hideMenu(level + 1); }
            	
            	if (cur_menu[level] != null) {
            	    if (level == 1) {
                	    menu1swapImg(cur_menu[1],false);
                    } else if (level > 1) {
                        var submenu = document.getElementById("nav" + level + "_" + cur_menu[level]);
                        if (submenu != null) {
                        	submenu.style.visibility = "hidden";
                        	submenu.style.display = "none";
                        }
                        cur_menu[level] = null;
                    }
                }
            }

            function menu1swapImg(id,make_hi) {
            	if (!isDOMcompliant()) { return; }
                var menuimg = document.getElementById("img_menu1_" + id);
                var cur = ""; if (cur_menu[0] == id) { cur = "-cur"; }
                var hi = ""; if (make_hi) { hi = "-ovr"; }
                if (make_hi) { cur_menu[1] = id; }
                menuimg.src = "../WebImgs/MenuBar/" + id + cur + hi + ".gif";
                if (!make_hi) { cur_menu[1] = null; }
            }
            
            function hideAll() {
            	if (!isDOMcompliant()) { return; }
            	hideMenu(3);
            	hideMenu(2);
            	hideMenu(1);
            }
            
            function initializePage(nav1,nav2,nav3) {
            	if (!isDOMcompliant()) { return; }
            	// swap in ovr graphic for menubar
            	if (nav1) {
            	    cur_menu[0] = nav1;
            	    menu1swapImg(nav1,false);
            	}
            	// populate spine
            	var spineimg = document.getElementById("spine_img");
            	spineimg.src = "../WebImgs/Spines/Spine-" + nav1 + ".gif";
            	if (nav2) {
            	    var n2td = document.getElementById("td_nav2_" + nav2);
            	    // insert "you are here" here (and for nav3 below)
            	}
            }
            
            function isDOMcompliant() {
            	return document.getElementById && document.getElementsByTagName;
            }