If you are not already using kramdown, Jekyll 3.0.0's default Markdown processor, then you must update your Markdown processor in your _config.yml file.

GitHub Pages only supports kramdown as a Markdown processor.

GitHub-flavored Markdown is supported by kramdown by default, so you can use Markdown with GitHub Pages the same way you use Markdown on GitHub.

Tip: If you're currently using Markdown processors that support GitHub-flavored Markdown, such as Rdiscount or Redcarpet, then you don't need to change your Markdown files for them to render properly.

If you're using a Markdown processor other than Kramdown, then you must change the Markdown setting in your site's configuration file.

  1. On GitHub, navigate to the main page of the repository.

  2. In your repository, browse to _config.yml.

  3. In the upper right corner of the file view, click to open the file editor. open file editor with edit icon
  4. Find the line that starts with markdown: and change the value to kramdown. markdown value in config.yml
  5. At the bottom of the page, type a short, meaningful commit message that describes the change you made to the file. Commit message for your change

  6. Below the commit message fields, decide whether to add your commit to the current branch or to a new branch. If your current branch is master, you should choose to create a new branch for your commit and then create a pull request. Commit branch options

  7. Click Propose file change. Propose file change button

For more information on using kramdown, see kramdown's quick reference guide or kramdown's official documentation.