This version of GitHub Enterprise will be discontinued on 2022-09-28. No patch releases will be made, even for critical security issues. For better performance, improved security, and new features, upgrade to the latest version of GitHub Enterprise. For help with the upgrade, contact GitHub Enterprise support.
Creating a custom 404 page for your GitHub Pages site
You can display a custom 404 error page when people try to access nonexistent pages on your site.
Adding a theme to your GitHub Pages site using Jekyll
You can personalize your Jekyll site by adding and customizing a theme.
Troubleshooting Jekyll build errors for GitHub Pages sites
You can use Jekyll build error messages to troubleshoot problems with your GitHub Pages site.