Ни 1 способ не работает...
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<script type="text/javascript">
function main()
{
var t = document.querySelector('table')
alert(t.lastChild.innerHTML)
alert(t.firstChild.innerHTML)
alert(t.firstElementChild.innerHTML)
alert(t.lastElementChild.innerHTML)
alert(t.childNodes[1].innerHTML)
alert(t.children[1].innerHTML)
}
document.addEventListener('DOMContentLoaded', main)
</script>
</head>
<body>
<table>
<tr>
<td>1</td>
</tr>
<tr>
<td>Нужен этот элемент</td>
<td>3</td>
</tr>
</table>
</body>
</html>