<html>
<head>
<style>
div { background-color:green; height:1em }
div:nth-child(-2n+1) { background-color:red }
div:first-child { background-color:green }
</style>
</head>
<body>
There should be only green below.  If you see RED the test has failed.
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div><div></div>
<div></div>
<div></div><div></div>
<div></div>
<div></div><div></div>
<div></div>
<div></div><div></div>
<div></div>
<div></div><div></div>
<div></div>
<div></div>