[CForms]When using fi:groups with style "tabs" calender select is behide the layer

[roy huang]

Hi,All:
    When using fi:group with styling "tabs" like:
    <fi:group>
     <fi:styling type="tabs" />
    If there has widget which its type is datetime,the calendar select box is under 
the tab div.So you can't select date from the calendar select.

    My environment:
    cocoon 2.1.5.1
    IE 6

   I think it is a bug,can anyone fix it ?
   

Roy Huang.