rem: getWebNavigation().goBack(); 
add: try { getWebNavigation().goBack(); } catch(ex) { } 
context: function BrowserBack(){  getWebNavigation().goBack();  UpdateBackForwardButtons();}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/c78295cd8240ace248a5196e5564551e02891ad8/navigator.js/buggy/xpfe/browser/resources/content/navigator.js