The are several controls available to end user, while viewing page in "Content Mode":
- button for changing value of the content block
- toolbar for page revision control (draft approve, etc.)
- button for viewing page-specific properties
All of mentioned controls have
z-index value associated with them to be above any element on the website. This unfortunately isn't good enough, when website has floating header and toolbar (item 2) should be above it, but any button (item 1 and item 3) should be below it.
Place the gaps between used z-indexes to add room for customization.