I found an error in httpd/error_log:
[Mon Dec 04 09:44:52.099171 2017] [rewrite:error] [pid 2498] [client XX.XX.XX.XX:43252] AH00670: Options FollowSymLinks and SymLinksIfOwnerMatch are both off, so the RewriteRule directive is also forbidden due to its similar ability to circumvent directory restrictions : /var/lib/nethserver/vhost/board/
Yes... I have a .htaccess file! My bad, I didn't think it before.
When I rename this file I can see the good website. So NS is ok!
But I need this feature, I have to learn more about rewriting...
It's ok, I've just add this line in the .htaccess and all is OK: