rem:  if (doc.documentURI.indexOf("about:neterror") == 0) return true;   return (doc.styleSheets.length && doc.styleSheets[0].href == "chrome: || (doc.styleSheets.length > 1 && doc.styleSheets[1].href == "chrome: 
add: return FBL.isSystemURL(win.location.href); 
context: this.isSystemPage = function(win)  // TODO combine with isSystemURL{    try    {        var doc = win.document;        if (!doc)            return false;        if (doc.documentURI.indexOf("about:blank") == 0)            return true;        // Detect network error pages like 404        if (doc.documentURI.indexOf("about:neterror") == 0)            return true;        // Detect pages for pretty printed XML        return (doc.styleSheets.length && doc.styleSheets[0].href                == "chrome://global/content/xml/XMLPrettyPrint.css")            || (doc.styleSheets.length > 1 && doc.styleSheets[1].href                == "chrome://browser/skin/feeds/subscribe.css");    }    catch (exc)    {        // Sometimes documents just aren't ready to be manipulated here, but don't let that        // gum up the works        ERROR("tabWatcher.isSystemPage document not ready:"+ exc);        return false;    }}
meta: 7450	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/7450/fd3fa7073b03b34b49adc8add0f84b5b4e33907f/lib.js/buggy/extension/content/firebug/lib.js