Javascript not working in Safari and chrome, works perfectly in IE and firefox

hi everyone, this is my 1st post here in this community forum, just would like to say "HI" to everyone.

i would like to share with you my experience in developing multiple dependency selection form developed in java script, how this script works is that when 1st selection is selected, based on the value the user select, a second level selection will appear and so on.

below is the Java-script code along with my form code too

Javascript:
<script type="text/javascript">

function nextSelect(o) {

if (o.value == '0') {
var next = o.nextSibling;
while (next && next.nodeName != 'SELECT') {
next = next.nextSibling;
}
next.length = 0;

return;
}
var d = document;

var useSelect = d.getElementById(o.name + '_' + o.value);

if (!useSelect) {
alert('Unknown id: ' + o.name + '_' + o.value);
return;
}

var copy = useSelect.cloneNode(true);
copy.style.display = 'inline';

var next = o.nextSibling;
while (next && next.nodeName != 'SELECT') {
next = next.nextSibling;
}
next.parentNode.insertBefore(copy, next);
next.parentNode.removeChild(next);
}
</script>

my form:
<div style="display: none;">

<!-- ##### First Selection ####### -->

<select name="second" id="first_dp" onchange="nextSelect(this);">
<option value="0">Choose</option>
<option value="dp_2_38">2 3/8'</option>
<option value="dp_4">4'</option>
</select>

<select name="second" id="first_hw" onchange="nextSelect(this);">
<option value="0">Choose</option>
<option value="hw_3_12">3 1/2'</option>
<option value="hw_4">4'</option>
</select>

<!-- ####### 2nd Selection ####### -->

<select name="third" id="second_dp_2_38" onchange="nextSelect(this);">
<option value="0">Choose</option>
<option value="dp_2_38_4.85">4.85 lbs/ft</option>
<option value="dp_2_38_6.65">6.65 lbs/ft</option>
</select>
<select name="third" id="second_dp_2_78" onchange="nextSelect(this);">
<option value="0">Choose</option>
<option value="dp_2_78_6.85">6.85 lbs/ft</option>
<option value="dp_2_78_10.4">10.4 lbs/ft</option>
</select>

>>>>>>and so on till 3rd selection<<<<<<<<<

</div>

<form action="pdfHandle.php" method="post" id="pdfsearch">
<fieldset>
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="142" height="146">
<p>
Type:<br />
Size:<br />
Weight:<br />
</td>
<td width="266"><select name="first" onclick="nextSelect(this);">
<option value="0">Choose</option>
<option value="dp">Drill Pipe</option>
<option value="hw">Heavy Weight</option>
</select><br/>
<select name="select">
</select>
<br/>
<select name="select">
</select>
<br/>
<select name="select">
</select>

</td>
</tr>
</table>
<p>
<input type="submit" name="submit" id="submit" value="Create PDF" />
<input type="reset" value="Reset Selection" />
</p>
</fieldset>
</form>
-----------------------------------------------------------------------

i would like to know what i am missing here and what is making Safari n chrome not to run this page properly, when u execute this code, only the 1st selection will appear while the rest of the selections are Null, i hope someone will guide me through this or direct me to solution or any other way of doing this perhaps

i thank you for viewing this post.