http://stovoxeobzeebmcgomjymnk73vcarxkikwo26lvfbaxmxbtjbe7umnid.onion/questions/491052/minimum-and-maximum-value-of-z-index
This was raised to the 32-bit standard in Safari 4 so it's only a concern if you're targeting older browsers. Also, even in Safari 3 anything above 16777271 gets capped at that, so unless you're using absurdly large z-index values to order multiple elements you shouldn't have a problem (i.e. setting one element to a z-index value of 2147483647 will ensure that element stays at the very top in any browser, unless it's competing with another element that...