Help using CSS overflow property

I have a checkBoxGroup with lots of items, so I'd like to use the CSS overflow property to display a vertical scroll bar. When I was using NetBeans 5.5.1 I did it using a panelGroup (code below), but with  NetBeans 6.1 it doesn't work. I also would like to use overflow with the Table component.

<webuijsf:panelGroup binding="#{SolicitacaoAtendimentoTecnico.groupPanel2}" id="groupPanel2"
                            style="height: 115px; left: 180px; top: 54px; overflow: auto; position: absolute; width: auto" styleClass="Lst_sun4">
                            <webuijsf:checkboxGroup binding="#{SolicitacaoAtendimentoTecnico.checkboxGroupModulosContratados}"
                                id="checkboxGroupModulosContratados" items="#{SessionBean1.modulosContratados}" required="true"
                                selected="#{SessionBean1.modulosSelecionados}" tabIndex="1"/>
                        </webuijsf:panelGroup>

Thanks for any help,
Felipe