If you can see this page, then the people who own this host have just activated the Apache Web server software included with their OpenBSD System. They now have to add content to this directory and replace this placeholder page, or else point the server at their real content.
The Apache manual is available with distribution as part of the
man file set,
and installed in /usr/share/doc/html/httpd.
Especially read the SSL documentation carefully within the manual, in addition to the ssl(8) and httpd(8) manual pages.
You are free to use the image below on an Apache-powered web server.
You can also use the image below on an OpenBSD-powered web server. Many other OpenBSD images are also available.
These images are also appropriate for a webserver using mod_ssl with OpenSSL cryptography.