Something I recently found out was you serve your GitHub repositories on your github.io domain like so: <username>.github.com/<repository-name>. So I have matthewroach.github.io and I wanted to add a page for one of repositories so people could see a demo of the code. After some time just waiting for GitHub to deploy the page it was beginning to fell like I was missing a piece of the puzzle. The site matthewroach.github.io was all working, but trying to visit the project page: matthewroach.github.io/react-placeholder was giving me 404. After some searching around I was not getting my info on what I was missing then I discovered there is a setting inside of the repository settings to turn on GitHub pages for repository. My guess is that I was using the Master branch, this leading it to not be active by default. Quick switch in the settings to tell it to use master and within minutes I could see my project page in all it’s glory.