I've recently created another account on GitHub to host stuff that I didn't want to associate with my main account. I've used an email address under my domain name and verified it and everything went well. I was able to create repositories, push code, set up an SSH key, edit my profile and so on.
But then if I try to open the account profile or any of the repositories while not logged in GitHub just acts as if the account doesn't exist and returns a 404.
I tried again a month later and the same issue persisted. I've seen other people complaining about the same issue, for example, https://old.reddit.com/r/github/comments/14htv2n/github_profile_returns_404/.