Hi !
Env.
Jboss Portal 2.6.2
Jboss AS 4.2.2
I read the docs on how to handle errors in my portal it states:
http://docs.jboss.com/jbportal/v2.6/referenceGuide/html_single/#d0e3411
The JavaServer Pages have to be located in the jboss-portal.sar/portal-core.war Web Application.