I use samba3.0(red hat 9) to share files with friends.

I set one directory permission is uploadable and readable,
because the directory is writable,
users can change file permissions in this directory.
after changing the permissions, users can delete the file.
how to set the right files permissions?

and i find using smb://my_ip_address cannot access samba server in
linux(red hat 8 & 9, or fedora)
but using command mount is ok
somebody can tell me the reasons?

thank you advanced.