Welcome to MR!!
It looks like you are putting an <hr/> tag in an incorrect location. It should be all by itself, not embedded inside a <p> or <div> tag.
Code:
Wrong:
<body>
<div>yadda yadda. <hr/></div>
<p>yadda yadda. <hr/></p>
<span>yadda yadda. <hr/></span>
</body>
Correct:
<body>
<div>yadda yadda.</div>
<hr/>
<p>yadda yadda.</p>
<hr/>
</body>
Also, make sure you are properly closing the tag <hr/> not <hr>.
If that doesn’t fix the problem, could you post the section of html that is causing the problem, not just the error code.
Cheers!