Hi,
You could edit the ZONE properties of first pane - > and go to:
1) Zone container -> Container -> New
code should be:
<div class="<%ContainerCssClass%}">
.. webpart ..
</div>
2) Zone container -> Container CSS class -> "add you css class here"
On the other panes you can reuse the container you just created, you just need to update the css class.
Hope this helps you.