This is gorgeous:
Upon checking src of this image, that's what I found:
file://cdn.sstatic.net/Content/Sites/stackexchangemeta/img/404.png
If anything, it shouldn't start with file://
... though it is still not found even if you put a proper protocol
Should this be /Content/Sites/stackexchangemeta/img/404.png
(i.e. on the same domain)? At least this one resolves properly. So, there's a wild file://cdn.sstatic.net
that snuck in 🤯