Check out example codes for "how to comment out html". It will help you in understanding the concepts better.

Code Example 1

Insert a single-line, or multi-line comment. 
Comments are designated by the tags <! -- and -->

Use the comment function to hide scripts on unsupported browsers
. If you are programming in JavaScript or VBScript, 
you can use the comment function to hide the script on browsers 
that don't support it. Insert the comment at the start of the 
script, and end it with //--> to ensure that the script works 
on browsers that do support it.

Code Example 2

<!-- This text is commented in html -->

Code Example 3

<!-- a comment in html -->

Code Example 4

<!--This is a comment. Comments are not displayed in the browser-->

<p>This is a paragraph.</p>

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