自己尝试HTML和CSS程序

I am making a try it yourself HTML and CSS program, like you would see on w3schools or other websites. I was wondering if there was a way to make another button that would just display the HTML and ignore the CSS instead of having to have the user type in both. Here is the code that I have, so I still want to make a toggle button that toggles the CSS off and on, but I am unaware on how to do this.I am making a try it yourself HTML and CSS prog