[pattern]

My main takeaway was the following:

    Z-index only works on positioned elements. If you
    try to set a z-index on an element with no position
    specified, it will do nothing.

I know I have scratched my head in the past trying to get z-index do what I want, and this knowledge probably would have helped!

[Hansi]

Agree, I remember that it took me a while to figure this out when I first tried playing with z-indexes.