Check out example codes for "which is right <hr> or <hr/> in html". It will help you in understanding the concepts better.

Code Example 1

<hr> <!--   it represents a horizontal line break, in HTML4.0 we use <hr>, 
            in XHTML1.0 we use <hr/>,  in HTML5(which is the current version of 
            HTML) we can use both <hr> and <hr/>    
       -->

Code Example 2

<!-- code -->

<hr>

<!-- code -->

Code Example 3

<h1>HTML</h1>

 <p>HTML is a language for describing web pages.....</p>


 <hr>

<h1>CSS</h1>

 <p>CSS defines how to display HTML elements.....</p>

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