<!-- <h1>Hello World</h1>
<!-- <h2>CatPhotoApp</h2>
<p>Kitty ipsum dolor sit amet, shed everywhere shed everywhere stretching attack your ankles chase the red dot, hairball run catnip eat the grass sniff.</p> <!-->
Your browser information:
User Agent is: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36.
So, to comment is to place the comment wrapper around the code you want to comment or simply place the comment wrapper around text you want to leave in place as a comment.
<!--
<h1>This is commented code</h1>
-->
<!-- This is a text comment -->
Now to uncomment simply remove the comment wrapper <!-- --->