Designer Serialization Problem

[Khoi Pham]

I've written a custom web control that exposes two panel controls as inner
properties. I can add content in html and then have everything render
correctly when I switch designer mode in visual studio. However, when I
switch back to Html view, the inner content is deleted entirely.

I've added the following attribute to the property but, this doesn't have
any affect..

[ DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]

Could anyone please provide insite?
Thanks,
-Khoi