Question about running this program on my desktop: Firefox

I have complete the Flipboard project and would like to try to run the code from my desktop and on firefox browser. I have copy and pasted the code to three files in Notepad++ and save each as their respective file names and types: index.html, style.css, app.js.
I am able to get the page to load and the style sheet to work, but the arrow and slide do not function. I have not changed anything in the files.

Any suggestions on what to check?