Same here in Firefox. The website configuration is broken.
The https site returns 404 but the http site has the content. This breaks Firefox's preferences for https, as I keep get redirected from the http to the https site since the https site responds (albeit with a 404).
It might not help you, but the link is working for me.
The site's https site is broken so those of us who have enabled Firefox's preference for https are getting 404s.
Useful to know ... thanks.
It is intentionally so. Go to the site root to see.