Here's the solution:
Edit the web.xml in
<!-- 404 SC_NOT_FOUND -->
just after </welcome-file-list>
Then the html and supporting files (images, css, etc.) go in
Works great with Firefox and Opera.
In Internet Explorer the 404 page doesn't show up though.
I read somewhere that if I enable "listings" in web.xml might work, but I just tried it and still doesn't work.
Any ideas there?