Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<head>
<style> 
p:empty
{
width:100px;
height:20px;
background:#ff0000;
}
</style>
</head>
<body>

<p></p>
<p>A paragraph.</p>
<p>Another paragraph.</p>

</body>
</html>

Result:

W3Schools.com - Try it yourself

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