It is not according Google, it is according Firefox. Who knows what IE says. Now what would be a definite independent technical proof? Because 'from hear saying' is not a really strong argument.
ok.. let's make a recap:
1) if you go to
https://IP the traffic is encrypted so it is secured.. pretending the browser to accept the certificate is quite silly because certificate doesn't know anything about IP (see above).. so, there's no technical reason to say it's unsecure
2) if you go to
https://FQDN but the certificate is a self signed one, again, the traffic is encrypted and so it is secure
3) if you have a site driven by, let's say, wordpress and you open it via https but some elements (images) are linked using http, your browser will tell you that the site is unsecure because of mixed content.. but https traffic is encrypted, so it is secure
now.. what's the point? what are you afraid of? MITM? you'll never know, never
you can't know what is right out there, the only things you can do is use your brain and trust.
there's no need of indipendent technical proof.. how things work is clear