W3C CSS2 Cascading Style Sheets, level 2 - instructional media + ...

9.9.1 Specifying the stack level: the ’z-index’ property
’z-index’
Value: auto | | inherit
Initial: auto
Applies to: positioned elements
Inherited: no
Percentages: N/A
Media: visual
For a positioned box, the ’z-index’ property specifies:
1. The stack level of the box in the current stacking context.
2. Whether the box establishes a local stacking context.
Values have the following meanings:
This integer is the stack level of the generated box in the current stacking
context. The box also establishes a local stacking context in which its stack
level is ’0’.
auto
The stack level of the generated box in the current stacking context is the
same as its parent’s box. The box does not establish a new local stacking
context.
In the following example, the stack levels of the boxes (named with their "id"
attributes) are: "text2"=0, "image"=1, "text3"=2, and "text1"=3. The "text2" stack
level is inherited from the root box. The others are specified with the ’z-index’
property.
Z-order positioning
.pile {
position: absolute;
left: 2in;
top: 2in;
width: 3in;
height: 3in;
}
This text will overlay the butterfly image.
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