Does these two attribute allow using resource outside the context??
One more thing, I have just seen that errorPage can be static objects(JSP 2.0 spec 3-79). That means even html that don't have a isErrorPage page directive can be set. Is it right?
Don't know the answers to the questions related to error-page, but standard forward and icnlude actions doesn't allow referencing resources outside the context. For this purpose you can use c:import JSTL action