You can display a custom 404 error page when people try to access nonexistent pages on your site.

  1. Navigate to your GitHub Pages repository.
  2. Switch to the master branch for a User/Organization Pages site, or to the gh-pages branch for a Project Pages site.
  3. Create a HTML file named 404.html or create a new Markdown file named 404.md at the root level of your GitHub Pages repository.
  4. In the YAML front matter of your new 404 file, add permalink: /404.html.
  5. Add the content you want to display to lost souls and weary travelers.
  6. Commit your changes and, if you're working on a local clone of your repository, push them up to GitHub.