You can add comments to your (X)HTML documents in order to remind yourself (or future editors) what you were trying to achieve with your (X)HTML tags. These comments only appear when the document is opened with a text editor. They are invisible to visitors in the browser.
To add comments to your HTML page:
Figure 3.23. Comments are a great way to add reminders to your text. You can also use them to keep track of revisions.
Figure 3.24. Comments are invisible (though they readily appear when the source code is displayedsee page 53).