Refer to
http://tracker.zkoss.org/browse/ZK-182

After add frozen, there should still be a scrollbar.
But in FF3, it just disappear.
In FF4, Chrome, it works well.

<zk>
<button label="add Frozen ">
<attribute name="onClick"><![CDATA[
Frozen fz = new Frozen();
fz.setColumns(1);
grid.appendChild(fz);
]]></attribute>
</button>
<button label="delete Frozen ">
<attribute name="onClick"><![CDATA[
grid.getFrozen().detach();

]]></attribute>
</button>
<grid id="grid" width="300px">
<columns>
<column label="column ${each}" forEach="1,2,3,4,5"
width="100px" />
</columns>
<rows>
<row forEach="1,2,3,4,5">
<label value="item ${each}" forEach="1,2,3,4,5" />
</row>
</rows>
</grid>
</zk>