CSS :empty Selector
HTML 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>
HTML View
A paragraph.
Another paragraph.