You can unpublish your GitHub User Pages site if the content is no longer relevant or you no longer want it to be publicly available.
To unpublish your User Pages site, delete either the
masterbranch in your
username.github.iorepository, or the entire
username.github.iorepository. For more information, see "Deleting unused branches" or "Deleting a repository."
If there is a custom domain enabled for the site, update your DNS settings. For more information, see "Using a custom domain with GitHub Pages."