How to run jekyll using c9??

$ jekyll serve --host $IP --port $PORT --watch

When your new post is not availalbe in your server, you should check some things.

• The post is not placed in the _posts directory.
• The post has incorrect title. Posts should be named YEAR-MONTH-DAY-title.MARKUP (Note the extension too.)
• The post’s date is in the future. You can make the post visible by setting future: true in _config.yml (documentation)
• The post has published: false in its front matter. Set it to true.
• The title contains a : character. Replace it with &#58.

these tips are originally found in here