I was not able to get on using firefox.I was finally able to get on using chrome, but it was not straight forward. I think it may have something to with my security settings and security plug-ins. Even with chrome it tells me that it is "not a secure site."
Your problems may be related to his now atypical server structure, in which "http://path" doesn't access the same content as "https://path":
"This is the HTTPS server at Jeffrey's machine; Jeffrey's public-facing content is on his HTTP server: http://regex.info/.
"(My HTTP and HTTPS trees have been separate for decades; a browser feature that automatically assumes that all HTTP servers have an identical HTTPS server is making some very big, and in this case, wrong, assumptions.)"
His content is all accessed via HTTP, not HTTPS, which is why browsers flag the site as "not secure", though in practice, since it serves static, non-personalized content, it's as secure as most other sites.