<html>
<head>
<style>
p:nth-child(3n+0)
{
background:#ff0000;
}
</style>
</head>
<body>
<h1>This is a heading</h1>
<p>The first paragraph.</p>
<p>The second paragraph.</p>
<p>The third paragraph.</p>
<p>The fourth paragraph.</p>
<p>The fifth paragraph.</p>
<p>The sixth paragraph.</p>
<p>The seventh paragraph.</p>
<p>The eight paragraph.</p>
<p>The ninth paragraph.</p>
<p><b>Note:</b> Internet Explorer 8 and earlier versions do not support the :nth-child() selector.</p>
</body>
</html>