Further question ... it appears that I can add a section in the jenkins.war web.xml as follows:
<error-page>
<error-code>404</error-code>
<location>/jspsnoop/ERROR/404</location>
</error-page>
I don't like have to open the war file and modifying it, but it is unclear is there is another way to customize the error code handling. I would like to redirect it to the login page. I have a situation where many of my customers are complaining about getting a 404 when they select the build output link embedded in the email. It would seem if they are not authorized to see the page that they would be redirected here. Not sure how to set location in this case.
Seems like this became more of an issue when I started using the folder plugin. I also use role base strategy. Any help in how to get around this would be greatly appreciated.