"Under what circumstances would I ever want my file permissions to read
anything other than "rwx------"?

With this configuration I can do anything to/with my own files, and no
one else can do anything to or with them.

Specifically:

1.  I understand that files I place on my web page must have more
liberal permissions if I want anyone else to be able to use them.  So,
what should these permissions be, and should they apply only to
individual files within directories, or to entire directories?  (Plain
language and examples, please.)

2.  At one time we were told that certain mail files/directories had to
be "world readable", whatever that means.  Is this true?  If so, exactly
what does it mean and to exactly which files/directories does it apply?
(Ditto.)

3.  What about the hidden files like .cshrc etc.?