What is the use of this syntax: <!---->? - html

Question

I've been working with the design UI of our website and looking for some templates available in the web.
Then I encountered with this syntax <!----> and I'm not familiar with it.
Can you please tell me what is it and what is it used for?
thank you.

Answer 1

As the other posts have mentioned the <!----> code in HTML is used for adding comments - a note left in the code by a developer with some info for other developers, or to remember something themselves. This code is viewable in the source but not displayed when viewing the HTML in the browser. Ex:
<!-- We need to update this each year -->
<div>© 2009 - 2016</div>
will produce:
© 2009 - 2016
In most cases the comment can be removed with no side-effect on the code. It's simply a note for developers.
Other Uses
Commenting Out Code
In addition to comments you'll sometimes see HTML code wrapped by <!---->. Ex:
<!-- Add this later
<img src="article.jpg" alt="Article">
-->
The above code will remove the entire image tag from the browser view. This is useful if you want to temporarily remove some HTML from a page, for testing/debugging or for later use. You'll sometimes see entire HTML sections commented out.
Conditional Code
Another common use of comments is to add conditional code used by specific browsers. The following snippet of code would only be read by Internet Explorer 8, and would apply a black background color to the body.
<!--[if IE 8]>
<style>
body {
background-color: black;
}
</style>
<![endif]-->
Website Builders
Some website builders generate their own code comments for internal use. For example, if you use Squarespace the generated code will contain comments like:
<!-- This is Squarespace. --><!-- www -->
These snippets, in some cases, are used by the generators themselves as a marker for inserting other code.
Build Scripts
There's a small chance the comment tag is being used as part of a build script, and in this case removing it would cause issues. Here's an example:
<!-- build:css -->
<link rel="stylesheet" href="css/normalize.css">
<link rel="stylesheet" href="css/main.css">
<!-- endbuild -->
The above code, used with a build system like Gulp and a Gulp plugin like HTML Replace will replace the content between the <!-- build:css--> and <!-- endbuild --> tags with new code. Removing either one of those comment tags will cause errors.

Answer 2

html comment tag
White space is not permitted between the markup declaration open delimiter(""). A common error is to include a string of hyphens ("---") within a comment. Authors should avoid putting two or more adjacent hyphens inside comments.
Reference : https://www.w3.org/TR/html4/intro/sgmltut.html
in that page goto 3.2.4 Comments title

Answer 3

this is an html comment tag.See this link below to know more
http://www.w3schools.com/tags/tag_comment.asp

Answer 4

This allows you commenting your html
<!--- my comment -->
(with --> to close it that's right)