I am just wondering how long does it take for GitHub page to show the new items that I have added to the repository.
I changed index.html
but after 10 minutes it still showed up the previous page...
The first time you generate your site it will take about 10 minutes for it to show up. Subsequent builds take only seconds from the time you push the changes to your GitHub repository.
However, depending on how your have your domain configured, there may be extra time for the CDN cache to break.
Note: using a subdomain, such as yourproject.github.io
is the recommended domain setup, but does mean page builds take longer to show up since it has the benefit of using the GitHub CDN.