VwpFAQLayoutFragAsChild
Page Fragment: Why can't I drag a page fragment into another component?
Page fragments can not be children of layout containers like grid, or group panel.
The rule (and the bug) is more general than that: No HTML component (e.g. non-JSF component) can be added as a child of a JSF component that has a rendersChildren property that is true. (This is the case for GridPanel, Table, and a few others).
