Control

With the same z-index of 10, whichever comes last in the DOM is on top.

IE6/IE7/IE8/Opera 9

Maximum value of z-index is 2147483647.

If it goes over 2147483647, it's converted to 2147483647.

Firefox

Maximum value of z-index is 2147483647 (same as IE).

If it goes over 2147483647, it's converted to 0 in FF3. In FF2, the element disappears.

In FF2, any element with a z-index < 0 also disappears.

Safari 3

Maximum value of z-index is 16777271.

If it goes over 16777271, it's converted to 16777271.