add:  if (active_languages.selectedIndex == 0) {  var moveUp = document.getElementById("up"); moveUp.disabled = true; }  if (active_languages_treeroot.childNodes.length > 1) {  var moveDown = document.getElementById("down"); moveDown.disabled = false; } 
context: function MoveUp() {  if (active_languages.selectedItems.length == 1) {    var selected = active_languages.selectedItems[0];    var before = selected.previousSibling    if (before) {      before.parentNode.insertBefore(selected, before);      active_languages.selectItem(selected);      active_languages.ensureElementIsVisible(selected);    }  }  UpdateSavePrefString();} //MoveUp
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/a2b8561d1cdb3b6ae2593f087b333c8adaa2c6d2/pref-languages.js/buggy/xpfe/components/prefwindow/resources/content/pref-languages.js