rem: button.removeAttribute("hidden"); 
add: button.setAttribute("hidden","false"); 
context:   Observe: function(subject, topic, prefName)  {    // verify that we're changing a button pref    if (topic != "nsPref:changed") return;    if (prefName.substr(0, this.domain.length) != this.domain) return;        var buttonName = prefName.substr(this.domain.length+1);    var buttonId = buttonName + "-button";    var button = document.getElementById(buttonId);        var show = pref.GetBoolPref(prefName);    if (show)      button.removeAttribute("hidden");    else      button.setAttribute("hidden", "true");  }
meta: 8395	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/8395/2755eaa923dfdccde003c3ce395ce923942ae2cb/navigator.js/buggy/suite/browser/navigator.js