Yes, thank you, 'chmod 755 web' removes the 403 error, and permits the default 'Welcome' page to load.
However, as I attempt to add sub-domains using ispconfig-3, the 403 error re-occurs at times. I'm not sure what I'm doing to trigger this. Do you know?
Anyway, I'll keep notes, and I might have other questions for you.
Thanks for pointing me at those pesky permissions.