"Securing your self-hosted website with Let’s Encrypt, part 7: a workflow to migrate from HTTP to HTTPS" has moved
You can now find it at /posts/2016/securing-your-self-hosted-website-with-lets-encrypt-part-7-a-workflow-to-migrate-from-http-to-https/. 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!