x
 
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="/jquery/jquery.js"></script>
<style>
  p, div { margin:5px; padding:5px; }
  .border { border: 2px solid red; }
  .background { background:yellow; }
</style>
</head>
<body>
<ul>
   <li>list item 1</li>
   <li>list item 2</li>
   <li class="third-item">list item 3</li>
   <li>list item 4</li>
   <li>list item 5</li>
</ul>
<script>
$("li.third-item").nextAll().andSelf().css("background-color", "red");
</script>
</body>
</html>