Custom Portal Error page for 500 Internal Server Error

We have employees who rarely access our Portals. There accounts are locked after 90 day's of inactivity. We would like to provide a more informative error page other than 500 Internal Server Error - com.sap.tc.webdynpro.services.exceptions.WDRuntimeException. I have accessed SAP Note 1718909 - Customizing default error pages for HTTP.

I am seeking the details for which areas in J2EEAPPS.SCA and EPBASIS.SCA require modfiication. Any examples or web links would be appreciated.

Cheers

Dan Mead