You can easily serve custom 404 error pages with Jekyll to replace the default 404 error page when people try to access nonexistent pages on your site. Any
404.html at the root of your
_site directory will be served automatically by GitHub pages and the local development server. Simply add a
404.html at the root of your site’s source and include front matter data to use the theme’s base layout like this:
--- layout: page title: 404 ---
Or if you plan to organize your files under subdirectories, the error page should have the following front matter data, set:
--- layout: default permalink: /404.html --- # 404 Page not found!