I have very little influence over the people who run the Apache server
I use. It always gives 403 (forbidden) when it fails to access a URL
with a tilde. That is, it never gives 404 (not found) for directories
that do not exist. Clearly this avoids giving anything away to
crackers. However, it also means it takes ages for the google.bot to
drop dead pages automatically.

Is this the default behaviour, or has the web master set it up? Can it
be changed if I work on the web master?

TIA,
Peter