Didn't expect an issue like this while I was learning XML. Please take a look at this site I am working on:
See the list with the scroll bars to the right? That is an XML file in an IFRAME. I haven't applied any formatting yet, but so far it seems to work fine.
Now hover over one of the menus above the IFRAME. The IFRAME content covers the dropdown menu. Originally the IFRAME content was another HTML page and worked fine.
Is there an explination for this behaviour?