<!DOCTYPE html>
<html>
<head>
<style>
p:only-child {
background-color: red;
}
li:only-child {
color: salmon;
}
b:only-child {
color: green;
}
</style>
</head>
<body>
<h1>Demo of :only-child</h1>
<div>
<p>This is a paragraph in a div.</p>
</div>
<div>
<p>This is paragraph 1 in a div.</p>
<p>This is paragraph 2 in a div.</p>
</div>
<p>Here are some <b>bold text</b>.</p>
<p>Here are some lists:</p>
<ul>
<li>First list item</li>
</ul>
<ol>
<li>First list item</li>
<li>Second list item</li>
<li>Third list item</li>
</ol>
</body>
</html>