2.1.52 [CSS-Level2-2009] Section 9.9.1, Specifying the stack level: the 'z-index' property
V0080:
-
z-index Value: auto | <integer> | inherit Initial: auto Applies to: positioned elements Inherited: no Percentages: N/A Media: visual Computed value: as specified For a positioned box, the 'z-index' property specifies:
§ The stack level of the box in the current stacking context. § Whether the box establishes a stacking context.
Quirks Mode and IE7 Mode (All Versions)
The initial value of the z-index property is 0.
IE8 Mode (All Versions)
The z-index property resolves large negative values (such as -2147483646) to 'auto'.
The z-index property accepts number values and percentage values instead of only allowing integers.
V0081:
-
Auto The stack level of the generated box in the current stacking context is '0'. The box does not establish a new stacking context unless it is the root element.
Quirks Mode and IE7 Mode (All Versions)
The auto
value is mapped to
'0' so that the initial value of the z-index property is '0'.
V0082:
-
The root element forms the root stacking context. Other stacking contexts are generated by any positioned element (including relatively positioned elements) having a computed value of 'z-index' other than 'auto'. Stacking contexts are not necessarily related to containing blocks.
Quirks Mode (All Versions)
Assigning an element a relative, absolute, or fixed position generates a stacking context.
IE7 Mode (All Versions)
Assigning an element a relative or absolute position generates a stacking context.