gepavlik,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script>
window.addEventListener('DOMContentLoaded', function() {
var li = document.querySelector('.captchaItem'),
parent = li.parentNode;
parent.removeChild(li)
});
</script>
</head>
<body>
<ul id="sortable">
<li>Item 1</li>
<li>Item 2</li>
<li>Item 3</li>
<li>Item 4</li>
<li>Item 5</li>
<li class="captchaItem">2</li>
</ul>
</body>
</html>