"404 - page not found" errors are what you get on a website when you click a link that takes to a page that no longer exists.
If you're here, the page you're looking for no longer exists, but you were redirected on purpose. That's not quite a 404. Might not that be a 403.9?
You've just found one of EventBuilder's easter eggs. Here's a 15-second video to commemorate the occasion.