I have a website hosted on a regular hosting with my own IP and I purchased COMODO SSL for a year via my hosting provider. I have a primary domain and couple of add-on domains. Add-on domains are completely different domains residing in separate folders of my primary domain (kinda like sub-directories).

I don't really need SSL all that bad. I would probably use PayPal which has its own secured interface for credit card online transactions. BUT...what I do need is to be able to login securely into my Joomla backends where I enter my admin credentials. Obviously, SSL that I have is connected to my primary domain (hoster doesn't provide SSL for add-ons anyway). The good news is that I'm somehow being able to
use SSL on my add-ons' backends. I force SSL in Joomla configuration for a backend of Joomla and it seems to be working fine. The only thing is...browsers show me a warning messages that I simply ignore since I know what it's about. The warning is because the certificate was issued for a different domain (ie. my primary one only).

The question is...anyone can explain it and do you think SSL would work fine for ALL of the domains (one primary and 2 add-ons)?