idea about showing correct/incorrect in guidelines more visually

Hi Harry.
First. Thank you for your great work with the Guidelines. Already donated :)

This Pull Request is only about showing the correct / incorrect examples more visually. As i couldn't compile the SASS locally i added a css file named pullrequest.css to the default.html template. 
You can check my proposal here: http://nevvkid.github.io/CSS-Guidelines/

Best. Johannes