[Locked duplicate] How to make the icons disappear

(Several hours ago, I posted the same question. And Ben Pleysier kindly gave me the solution. But it is working on me now.

I am posting again to learn other ways. It is an urgent issue to me now. Time is very tight.)

To make the icons disappear, I added the lines below to css.

153 .site-nav--icon {

              display: none;

       }

But it didn't work.

Link to Generico

And the message below pops up, before the file is opened.

Hosun Kang