When tabbox's orient is vertical, set a div tag with height=400 inside tabpanel, the actual visible part didn't match the height.
<zk>
<window title="Tabbox" border="normal">
<tabbox id="box" orient="vertical">
<tabs width="40px">
<tab label="input" />
<tab label="grid" />
</tabs>
<tabpanels>
<tabpanel>
<div height="400px" style="border: 1px red dotted;">input</div>
</tabpanel>
<tabpanel>
grid
</tabpanel>
</tabpanels>
</tabbox>
</window>
</zk>