How do I re-enable Firefox's “mixed ssl with non-ssl elements in page” warning?

Question

I accidentally pressed Enter when this warning first showed up on my freshly-installed system before having a chance to read it.

Now I'd like to have the warning back because I feel insecure. It's probably some setting in about:config, but I can't find it.

Thank you very much

Answer 1

In about:config, set the security.warn_viewing_mixed setting to True.