Page 54 - HTML5

Chapter 7: Comments

Introduction

Similar to other programming, markup, and markdown languages, comments in HTML provide
other developers with development specific information without affecting the user interface. Unlike
other languages however, HTML comments can be used to specify HTML elements for Internet
Explorer only. This topic explains how to write HTML comments, and their functional applications.

Syntax

• <!-- Comment text -->

Remarks

Anything starting with <!-- and ending with --> is a comment. Comments cannot contain two
adjacent dashes (--), and must end with exactly two dashes (i.e. ---> is not correct).

Comments are not visible on a web page and cannot be styled with CSS. They can be used by the
page's developer to make notes within the HTML, or to hide certain content during development.

For dynamic or interactive pages, hiding and showing content is done with JavaScript and CSS
rather than with HTML comments.

JavaScript can be used to get the content of HTML comment nodes and these nodes can be
dynamically created, added and removed from the document but this will not affect how the page
is displayed.

Since HTML comments are part of the page's source code, they are downloaded to the browser
along with the rest of the page. The source code can typically be viewed using the web browser's
menu option to "View Source" or "View Page Source."

Examples

Creating comments

HTML comments can be used to leave notes to yourself or other developers about a specific point
in code. They can be initiated with <!-- and concluded with -->, like so:

<!-- I'm an HTML comment! -->

They can be incorporated inline within other content:

<h1>This part will be displayed <!-- while this will not be displayed -->.</h1>

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