I don't know the technical reason, I don't 'do' technical in any shape or form, but I do know that the 's' stands for 'secure' and we can't access secure sites.
Ash runs the Webcomics List comic site and I can't access comic that say https, remove the 's' and I can open the comic OK.
Ash isn't avilable today but I'll check and post the answer as soon as I can.