Before we get too far, we need to learn how to add comments. A comment is a note to the developer. It is text within the source code that we do not want the computer to interpret. Every programming language has a concept of code comments, but the syntax required to denote a comment and set it apart from the rest of the source code is different in each programming language.
In HTML, we indicate that a line of text is a comment like this:
<!-- This sentence will not appear to the user. -->
The special opening tag <!-- marks the start of the text
to be ignored by the computer, and ends with -->.
Comments can last for several lines:
<!-- This sentence will not appear to the user.
Nor will this.
Or this.
-->
The other main purpose of code comments is to temporary disable some HTML code, perhaps as part of a debugging strategy:
<h1>Hello!</h1>
<!-- <a href="http://www.google.com">Search</a> -->
<h2>Goodbye!</h2>
Try that in your browser to confirm which code will be interpreted and which will not.
Using comments to temporarily disable a line of code is so common, you'll want to do it often.
In Atom, you can use the menu option Edit | Toggle Comments. But
hopefully you'll be using this technique so much that the keyboard
shortcut will become second nature, Cmd / (on Windows, CTRL /).