I cannot load this old HTML/JS website in any browser – how to see it again

A client hired me to rebuild their website that was created in 2008 or so. It is an .html site. At the time (about 6 weeks ago) it could only be opened in Firefox – it would not load at all in other browsers. That had been the case for sometime. Now we are ready to built out the site (it was just static pages with lists of resources and articles) but – uh oh! – now we cannot even see it in Firefox.

So I got into the Cpanel/File Manager and it looks like the index page is html but I think maybe the rest are .js files. Maybe this is why the site won’t load? I think I recently updated Firefox, so may that is why I can’t see it there now either?

I was thinking maybe I’d downgrade my Firefox – but I don’t really know what the issue is.

Any ideas about what is going on? And How I can see this site again – whether pubic or local – just so I can at least copy and paste this content out of it?