Using z-index
The first part of this article, Stacking without the z-index property, explains how stacking is arranged by default. If you want to create a custom stacking order, you can use the z-index property on a positioned element.
Свойство z-index может иметь значение в целых числах (положительные, ноль, или отрицательные), что представляет собой позицию элемента вдоль оси z. Если вы не знакомы с осью z, представьте себе страницу как стопку слоёв, имеющих собственное порядковое число. Слои представлены в числовом порядке, with larger numbers above smaller numbers.
- bottom layer (farthest from the observer)
- ...
- Layer -3
- Layer -2
- Layer -1
- Layer 0 (default rendering layer)
- Layer 1
- Layer 2
- Layer 3
- ...
- top layer (closest to the observer)
Примечание:
- When no
z-indexproperty is specified, elements are rendered on the default rendering layer 0 (zero). - If several elements share the same
z-indexvalue (i.e., they are placed on the same layer), stacking rules explained in the section Stacking without z-index apply.
In the following example, the layers' stacking order is rearranged using z-index. The z-index of element #5 has no effect since it is not a positioned element.
Source code for the example
HTML
html
<div id="abs1"> <b>DIV #1</b> <br />position: absolute; <br />z-index: 5; </div> <div id="rel1"> <b>DIV #2</b> <br />position: relative; <br />z-index: 3; </div> <div id="rel2"> <b>DIV #3</b> <br />position: relative; <br />z-index: 2; </div> <div id="abs2"> <b>DIV #4</b> <br />position: absolute; <br />z-index: 1; </div> <div id="sta1"> <b>DIV #5</b> <br />no positioning <br />z-index: 8; </div> CSS
css
div { padding: 10px; opacity: 0.7; text-align: center; } b { font-family: sans-serif; } #abs1 { z-index: 5; position: absolute; width: 150px; height: 350px; top: 10px; left: 10px; border: 1px dashed #900; background-color: #fdd; } #rel1 { z-index: 3; height: 100px; position: relative; top: 30px; border: 1px dashed #696; background-color: #cfc; margin: 0px 50px 0px 50px; } #rel2 { z-index: 2; height: 100px; position: relative; top: 15px; left: 20px; border: 1px dashed #696; background-color: #cfc; margin: 0px 50px 0px 50px; } #abs2 { z-index: 1; position: absolute; width: 150px; height: 350px; top: 10px; right: 10px; border: 1px dashed #900; background-color: #fdd; } #sta1 { z-index: 8; height: 70px; border: 1px dashed #996; background-color: #ffc; margin: 0px 50px 0px 50px; } Смотрите также
- Stacking without the z-index property: The stacking rules that apply when
z-indexis not used. - Stacking with floated blocks: How floating elements are handled with stacking.
- The stacking context: Notes on the stacking context.
- Stacking context example 1: 2-level HTML hierarchy, z-index on the last level
- Stacking context example 2: 2-level HTML hierarchy, z-index on all levels
- Stacking context example 3: 3-level HTML hierarchy, z-index on the second level