rem: backBroadcaster.setAttribute("disabled", !webNavigation.canGoBack); forwardBroadcaster.setAttribute("disabled", !webNavigation.canGoForward); 
add:      var backDisabled = (backBroadcaster.getAttribute("disabled") == "true"); var forwardDisabled = (forwardBroadcaster.getAttribute("disabled") == "true");  if (backDisabled == webNavigation.canGoBack) backBroadcaster.setAttribute("disabled", !backDisabled);  if (forwardDisabled == webNavigation.canGoForward) forwardBroadcaster.setAttribute("disabled", !forwardDisabled); 
context: function UpdateBackForwardButtons(){  var backBroadcaster = document.getElementById("canGoBack");  var forwardBroadcaster = document.getElementById("canGoForward");  var webNavigation = getWebNavigation();  backBroadcaster.setAttribute("disabled", !webNavigation.canGoBack);  forwardBroadcaster.setAttribute("disabled", !webNavigation.canGoForward);}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/8130400b54ddb2ad383a55c555256be82eb24012/navigator.js/clean/xpfe/browser/resources/content/navigator.js