For suppose, we are showing a popup when we click a button in a page, and that popup contains some validation.
If that validation fails, by default ,it will show Faces Message behind the popup.But we need to show that message on top of pop up.
We have a simple solution for that:
set modal = false for the dialog in the popup. It will automatically show the faces messages on top of the popup.
Oracle ADF n BPEL 
This is a stupid solution. I want the Faces message to come on top of my modal popup. The whole point of making my popup modal is to prevent the user to do any action on the main page – so removing the modal property is not a solution!
If you are displaying the message on top of popup, practically,u dont do anything on the parent page until u escape/close that popup.Moreover I’m giving this solution in the context of the simple way of displaying faces messages on top of popup.I dont want ur stupid comments at all…