Css or javascript problem?

Hi all,
I have a webpage that has ajax tabs. The css is all validated but when I enlarge the page in IE to biggest size then the last tab (“how we can help”) breaks at the largest setting. FireFox breaks after +2 text enlargements starting from the default size.

Here is the webpage:
[url]http://216.219.94.105/david1.htm[/url]

The gw_Tabpane css governs the offending css.
The linked javascript file is:
[url]http://216.219.94.105/js/tab-view.js[/url]

The ajax tabs are controlled by the following javascript:
<script type=”text/javascript”>
initTabs(‘gw_tabView1’,Array(‘Medarc Ltd.’,’National’,’International’, ‘How we can help’),0,680,0);
</script>

You can see the screen grabs:
Firefox:
[url]http://216.219.94.105/InEx.jpg[/url]
IE:
[url]http://216.219.94.105/FireFox.jpg[/url]

Why is this happening is it a css problem or a javascript one? Thanks for any help

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