how can a user add comments in html code example

Example 1: html comment

<!--HTML Comment Example! HTML Comments do not affect your code in
any way, comments can be used to take notes to yourself, or if you 
are working with a team, this could be a good way to communicate 
without messing up any of your code. Comments will not be shown 
in your HTML webpage. -->

Example 2: comment text in html

<div>
<p>This text is visible. Check the source code for multi-line comment.</p>
<!--  
Hello, world! I am a comment and I am
displayed in multiple lines!
--> 
</div>