As you can see in the test case (http://jsfiddle.net/lensco/J3PUq/) z-index doesn't seem to affect inline-block level elements with a rotateY transform. This happens only in Safari – tested in WebKit Nightly 7534.48.3 and Safari 5.1 on Lion and Safari 5.0.6 on Snow Leopard. Chrome (dev channel) looks fine.
Updated to remove -webkit-: Link - https://jsfiddle.net/2dsfqtrj/ I am able to reproduce this in Safari Technology Preview 153, where the second container does not work while hovering and shift similar to first container. All other browsers (Chrome Canary 107 and Firefox Nightly 106) have 'rotate' effect. Going to change status to "New", it might be duplicate of other bug but still sharing updated testing results. Thanks!
This is about 3d transform rendering.
<rdar://problem/122588208>