how to comment out html lines code example

Example 1: how to comment out html

<!-- a comment in html -->

Example 2: how to comment in html

<!-- This is HTML -->
/* This is CSS */
// This is CSS to

Example 3: html how to add comment

<!-- This is the first comment, it won't be shown on a page -->

<h1>And this is a header. It will be fully visible.</h1>

<!--
Multiline comment.
You can place a lot of information there.
Maybe even a whole book.
-->