Asking as a tech dummy. I don't think this belongs under technical support because it isn't really about this website, but about many. I could be wrong about that!
Some of the sites I visit often have that little lock symbol, as this one does. Some say "not secure", for example une femme dot net (don't want to link it in case there really is something wrong). It isn't about ads exactly, because some of the lock symbol ones still have ads.
Is there something wrong with the not secure ones? Several of my daily sites are listing that now and I just noticed it last week. Thanks for the education if you can help this dummy!