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-index property is specified, elements are rendered on the default rendering layer 0 (zero).
  • If several elements share the same z-index value (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;
}

See also