Owner: This website does not supply ownership information
This is used for EV certificates. In this case, Firefox will just copy the content of the O, L, ST and C RDNs in the Subject DN. It doesn't do it otherwise.
You can read more on the topic of EV certs in this answer for example. You'll notice that
https://www.google.com/ doesn't have one and shows this same message.
Verified by: Not specified
This seems to use the O RDN of the Issuer DN. Not having it isn't necessarily a big deal. When you chose (or when someone else made the decision) to trust that CA, it should have known where it came from. The CA cert's Subject DNs (which become Issuer DN) don't have a mandatory structure (EV certs are more strict on this, though). What matters is to have a DN that identifies the CA sufficiently, whether the CN or O RDNs are present doesn't matter that much, although it seems it would be better practice to have them (just from an administrative point of view).
Although these messages come with good intent, they tend to make things more confusing unfortunately. This is still the object of debate in a number of Firefox Bugzilla issues. Here are a couple:
Connection Partially encrypted
Parts of the page you are viewing were not encrypted before transmitted over the internet
This one is a problem. It means you have mixed content on your page, which is bad practice because you can't be sure what can and cannot be trusted as coming from the server (as guaranteed by SSL/TLS otherwise). It's probably loading images, scripts, iframes or making XHR requests via plain HTTP. In some cases, it can leak sensitive data this way.
You can find out which resources are loaded via plain HTTP on your page using the Firebug extension (Network tab). Chrome has something similar in its developer tools.