XFs default error pages are minimal and don't direct you anywhere or link back to the home page, or even redirect after 10 seconds or so - so I wondered if they can be modified, and if so, where would I do this?
Okay, so providing the requested_page_not_found phrase isn't altered during an XF update, the change I make will stick between updates.
Good to know.
PS. It would be nice for XF to come with at least a link back to the home page within the default error notice - at the moment it just plonks you on a minimal page with no obvious links back to the site home page in the body text.