Counting Using .childNodes In IE And Mozilla

I want to count the number of childnodes, when i run this script in mozilla i get a different total for the number of childnodes from numkids then when the script runs in IE. Why is this? How Can I get the same number. I want to loop though an objects child elements setting them to invisible or visible

<script type="text/javascript"><!--
function rec(n) {

var kids = n.childNodes;
var numkids = kids.length;

for(var i = numkids-1; i>=0; i--)
{

// sets child to hidden
alert(numkids);
alert(kids[i].nodeValue);
//kids[i].style.visibility = 'hidden'
}}

var a = document.getElementById('commentholder0');

// this function loops though the parts and makes then invisiable so you cant see them overlap
rec(a);

</script>

My html is here:

<ul id= "commentholder0" >
<li id="comment1">this is a test</li>
<li id="comment2">this 2 is a test</li>

</ul>