Newb doesn't understand why this JS works in FF, etc but not all IE

[Neil Snape]

Hi. I was happy when this little rollover effect was working on my MAcs all browsers. It is also working on all Windows Chrome, FF, Opera, Safari too, but only IE6. Funny I thought IE6 was the buggy Windows browser.

So the effect is to highlight spans in a list of non congruent Client Names
while hovering on the category links on the left div.

On IE8,7, 5 all are hiding allthe Client NAmes div. on hover

Here is the actual page:

http://corporate.fr/ce/clients.html

 <script type="text/javascript">
var category = document.getElementById('clientListNavBar');
category.onmouseover = function (e) {
    e = e || window.event;
    var targ = e.target || e.srcElement;
    if (targ.nodeType === 3) {
        targ = targ.parentNode;
    }
    if (targ.nodeType === 1 && targ.nodeName === 'A') {
        document.getElementById('clientList').className = targ.href.split('#')[1];
    }
    return false;
}
category.onmouseout = function (e) {
    document.getElementById('clientList').className = '';
}
</script>

Should I past the inline styles that are show / hide?