How can I prevent navigation rendering as list before the CSS and Javascript are applied?

I have navigation that is built with unordered list elements in HTML. I style it with CSS ( using PUREcss ). Jquery is used, as is a small JS function. These are the implementation instructions from PUREcss.

When the page loads, it always renders the list as normal html before rendering the navigation. What can I do to prevent the initial rendering of the list?