A "Level 1 Error" is represented by an exception which is thrown during rendering a view (as distinct from an exception thrown during an Action, which can be a "perfectly normal" part of its semantics, arising through, say, some sort of validation failure). RSF's response on receiving such an exception is to issue a redirect to the application's default view - this is in fact all that defines the default view as the default.

What makes this a "Level 1 Error" is that RSF sets a special request parameter in the redirected rendering of the default view to indicate this is an error redirect. If a *further* error occurs while rendering this error redirect view, RSF declares a "double fault", and renders a "fatal error page". You can customise this behaviour by implementing a FatalErrorHandler as application scope bean fatalErrorHandler. If your fatal error handler itself throws an exception, RSF will return to its hardwired default :P