The following code is working fine in Firefox, but not IE 7:

 <a4j:form>
 <a4j:commandButton action="#{ReferencePage.toggleDisplay}" reRender="footer" value="Toggle"/>
 <rich:dataTable value="#{ReferencePage.testRows}">
 <rich:column>
 <h:outputText value="Test Row 1"/>
 </rich:column>
 <f:facet name="footer">
 <rich:columnGroup>
 <rich:column id="footer">
 <h:panelGroup rendered="#{ReferencePage.display == true}">
 <h:outputText value="aaaaaa"/>
 </h:panelGroup>
 </rich:column>
 </rich:columnGroup>
 </f:facet>
 </rich:dataTable>


 </a4j:form>

.. which basically hides/shows the value "aaaaaa" in the footer when you press the button.

It's fine in firefox, but in IE, I get a Javascript error saying "Error: Type mismatch". Wish my JavaScript debugger in IE was working so I can tell more.

I think the JavaScript error only happens when you start with display = true (so "aaaaaa" shows on load), and you click the button to hide it. The text does hide, but you also get that javascript error.