rem: element = document.createElementNS(XUL_NS, "menuitem"); 
add: element = document.createElementNS(gXUL_NS, "menuitem"); 
context:   showOpenInTabsMenuItem: function (aTarget)  {    if (!this.validOpenInTabsMenuItem(aTarget) ||        aTarget.lastChild.getAttribute("class") == "openintabs-menuitem")      return;    var element = document.createElementNS(XUL_NS, "menuseparator");    element.setAttribute("class", "openintabs-menuseparator");    aTarget.appendChild(element);    element = document.createElementNS(XUL_NS, "menuitem");    element.setAttribute("class", "openintabs-menuitem");    element.setAttribute("label", BookmarksUtils.getLocaleString("cmd_bm_openfolder"));    element.setAttribute("accesskey", BookmarksUtils.getLocaleString("cmd_bm_openfolder_accesskey"));    aTarget.appendChild(element);  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/5d726a8d7b8ffd957682f360f58e73a7d277d96b/bookmarksMenu.js/clean/browser/components/bookmarks/content/bookmarksMenu.js