When using borderlayout, the width of text labels in the <west> and <east> components varies between browsers (or maybe it's the width of the <west> and <east> components themselves). This causes the text to be displayed in multiple lines in IE, but in one line on others (FF and Chrome).

Example that will demonstrate the issue:
<zk>
<borderlayout>
<west>Some long text on the left</west>
<center>Some more text in the middle</center>
<east>Some text on the right</east>
</borderlayout>
</zk>