On a Mac, running Firefox, why do I get a Microsoft error page?

I was on this site and clicked on the “Petrography Technician” link and got a Microsoft “can’t find that page” page. I’m using Firefox on a Mac and haven’t seen a page like that on my Mac before.

What is going on?

That page is generated by the site itself. Looks like that is what they use as their default 404 page, possibly because they are running an MS OS on their servers.

Thanks for the speedy answer.

That is the normal default error page for Microsoft IIS servers. It’s entirely unrelated to what browser you’re using.

The webpage url is duplicated, which causes the error. The actual page is
But for some reason it is listed like that twice in a row in your link. The error page you’re seeing originates on the server, which is running Microsoft software.