It is nice to observe how list of CSS properties supported by Prince is growing day after day Currently z-index property is not listed on documentation page but it looks like Prince supports z-index, did you miss it :?:

Prince does not support z-index -- what behaviour led you to believe that it did?

Just when I specified z-index for nested div elements on this page:
http://geocities.com/csssite/prince/bug02.xhtml
Prince formatted it properly, so I thought it supports z-index

div {z-index:1}
div div {z-idex:2;}

Ah, it looks as if the new test case works because it has an extra line in both the PASSED and FAILED sections; if you remove one line from each it displays in the wrong order again. Confusing, but it should be fixed once we implement the correct stacking order in Prince.

For the record, support for the z-index property has been added to Prince 5.0