You are able to see this document because of two things

the .htaccess file in this directory

AuthUserFile /usr/local/lib/htpasswd/passwd_ex2

AuthGroupFile /usr/local/lib/htpasswd/group_ex2

AuthName ExampleByGroup

AuthType Basic





<Limit GET>

require group html-users

</Limit>

  

the group file (kept elsewhere)

html-users: html sgml

  

and the password file (kept elsewhere)

This was generated by using

      htpasswd -c /usr/local/lib/htpasswd/passwd_ex2 html

      htpasswd /usr/local/lib/htpasswd/passwd_ex2 sgml