function toggleNav(id){
  menu = eval('document.getElementById("menu'+id+'")');
  menuclass = menu.className;
  if (menuclass == "hidden") {
    eval('document.getElementById("menu'+id+'").className = "visible"');
    eval('document.getElementById("nav-icon'+id+'").src = "/images/icon-collapse.png"');
  } else {
    eval('document.getElementById("menu'+id+'").className = "hidden"');
    eval('document.getElementById("nav-icon'+id+'").src = "/images/icon-expand.png"');
  }
}