Comment tags are used to insert comments in the HTML source code.
HTML Comment Tags
You can add comments to your HTML source by using the following syntax:
Notice that there is an exclamation point (!) in the opening tag, but not in the closing tag.
Note: Comments are not displayed by the browser, but they can help document your HTML source code.
With comments you can place notifications and reminders in your HTML:
<p>This is a paragraph.</p>
<!-- Remember to add more information here -->
Comments are also great for debugging HTML, because you can comment out HTML lines of code, one at a time, to search for errors:
<img border="0" src="pic_mountain.jpg" alt="Mountain">
You might stumble upon conditional comments in HTML:
.... some HTML here ....
Conditional comments defines some HTML tags to be executed by Internet Explorer only.
Software Program Tags
HTML comments tags can also be generated by various HTML software programs.
For example <!--webbot bot--> tags wrapped inside HTML comments by FrontPage and Expression Web.
As a rule, let these tags stay, to help support the software that created them.