security: code assumes that both private/ and public_html/ directories are served

[hwnlp-admin]

Normally one would run a server which serves only the pages in the public_html/ directory and other directories could be used on the server but not accessed from outside.

All directories currently lack index.html files, so the MACS server shows a list of the files in that directory (e.g. https://www2.macs.hw.ac.uk/~ctl2/Diss/backup/)