Minimum and maximum value of z-index?

http://www.w3.org/TR/CSS21/visuren.html#z-index

‘z-index’

Value: auto | <integer> | inherit

http://www.w3.org/TR/CSS21/syndata.html#numbers

Some value types may have integer
values (denoted by <integer>) or
real number values (denoted by
<number>). Real numbers and
integers are specified in decimal
notation only. An <integer>
consists of one or more digits “0” to
“9”. A <number> can either be an
<integer>, or it can be zero or
more digits followed by a dot (.)
followed by one or more digits. Both
integers and real numbers may be
preceded by a “-” or “+” to indicate
the sign. -0 is equivalent to 0 and is
not a negative number.

Note that many properties that allow
an integer or real number as a value
actually restrict the value to some
range, often to a non-negative value.

So basically there are no limitations for z-index value in the CSS standard, but I guess most browsers limit it to signed 32-bit values (−2147483648 to +2147483647) in practice (64 would be a little off the top, and it doesn’t make sense to use anything less than 32 bits these days)

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