My networking know-how is very superficial. Lately I have been using Comodo Dragon as my preferred browser. It seemed fine until the other day, but now, many (not all) HTTPS sites are being displayed as insecure. A few, including Geekzone, don't have this problem, but others do. A recent example is https://billbennett.co.nz/nz-wireless-rural-broadband/. On Chrome this displays normally, as secure. On Dragon I get a warning that it is not secure.
Does this have to do with Comodo security certificates not being up to date? I don't really understand what is going on here, or what could be causing this. For the moment I am using another browser that does not have this issue but I would like to know why Dragon is behaving differently in this regard.