Current design hasn’t been optimized for mobile yet.
Also for the Firefox issue, it might be because of tracking privacy software, like Ghostery or uBlock. For me it was a Firefox specific setting that was blocking third party JS from loading in the browser as a safety concern. Your console might tell you more. I will see if I can dig up the right article again.
Also are people still using Internet explorer? Isn’t Microsoft pushing people to Edge? I confirmed it’s running on Edge.