rem: getWebNavigation().goBack(); 
add: try { getWebNavigation().goBack(); } catch(ex) { } 
context: function BrowserBack(){  getWebNavigation().goBack();  UpdateBackForwardButtons();}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/e6ab922193cbeb49c5031b05b08730ab5850d09e/navigator.js/clean/xpfe/browser/resources/content/navigator.js