my website did not work on github code example

Example 1: my github page doesn't work

The preferred files to be served are index.html, index.md, and README.md, 
in that order. If none of these files exist, your website will show a 404 
Not Found error, even if there are other HTML files in the repository.

Example 2: github url not showing

git reset --hard refs/original/refs/heads/master