Problem : Negative values for z-index cause elements to disappear in Gecko browsers
I read that this is actually correct behavior, and the other browsers are wrong. But it seems kinda stupid to me.
Why would you ever use a negative number for the z-index if the object will not be displayed?
Is this really correct handling of negative z-axis values? If so, what’s the rationale?
Solution: Negative values for z-index cause elements to disappear in Gecko browsers
It is an alternate means of invisibility. An invisible element block mouse events to underlying layers but a layer hidden behind the background does not. It also allows effects with semi-transparent background-images; though I doubt there is support to actually do anything until CSS comes along. Finally it helps to simplify dynamic scripting that manipulates z-index, by giving a place the you know puts the layer out of sit.
