from Firefox PC works fine :)

My Firefox says for media-internal.mitmuseum.org where the images are hosted on

The certificate is only valid for the following names: *.s3.amazonaws.com, s3.amazonaws.com

Let's hope you happened to get served a valid cert, and not that the cert validation is disabled or broken in your Firefox.

Yep, Firefox is telling me that some parts of this page are not secure, such as images. I guess you may have more strict security settings.