All LINUX server based groups, Observatory and Institute Lorentz, have inside their personal home directory a directory name public_html, which is the top level directory of your personal WEBstack. Your personal webstack has a URL link http://home.INSTITUTE.leidenuniv.nl/~ACCOUNT, where INSTITUTE is either strw, physics or lorentz and ACCOUNT is the login name you use to access your personal desktop.
In order for the WEB server to read your public_html directory you ned to set the access rights of that directory to:
chmod 711 public_html
The WEB server reads in order the index.php or index.html file as the index to start out serving your WEBstack.