Blinded by the lights

Should you need to see the stack trace when an error on an APSX page hosted by Sharepoint occurs do the following:

• SharePoint\SafeMode: AllowPageLevelTrace="true" and CallStack="true"
• system.web\customErrors:mode="Off" or mode="RemoteOnly"

Yet the standard error page usually does not tell aything that can suggest the reason for the error…