404 Error on Page with GitHub publishing

I am trying to create a webpage to upload for a Coursera course and I have done the steps over and over again, created a repository, uploaded files and tried to keep the branches on the right setting and I keep getting a 404 error and it is driving me to the point where I want to say ‘f*** this s***’ and leave GitHub. All I have in the repository are HTML and CSS files with it keeps coming up with the same 404.