"Securing your self-hosted website with Let’s Encrypt, part 4: hardening default setups and avoiding known vulnerabilities" has moved
You can now find it at /posts/2016/securing-your-self-hosted-website-with-lets-encrypt-part-4-hardening-default-setups-and-avoiding-known-vulnerabilities/. If you don't do anything, you'll be redirected automatically (if your browser supports that).
Or you can update your bookmarks, if you still use such a thing!