RewriteEngine on
    RewriteCond %{REQUEST_FILENAME} -s [OR]
    RewriteCond %{REQUEST_FILENAME} -l [OR]
    RewriteCond %{REQUEST_FILENAME} -d
    RewriteRule ^.*$ - [NC,L]
    RewriteRule ^(srv|user)($|/) - [L]
    RewriteRule ^(.*) /path-to-client-page/index.html [NC,L]