The CSS reference

"z-index" - css property (v. css 2)

  • Indicates the stack order of an element
  • Initial value: auto
  • The property is not inherited
  • HTML usage: positioned elements
  • Browsers that support the z-index - property :
    Internet Explorer Mozilla Firefox Opera Google Chrome Apple Safari

Possible z-index values:

value Comments CSS
auto Follow the normal calculated stack order. 2
integer This integer is the stack level of the generated box in the current stacking context. The box also establishes a new stacking context. 2
inherit Will inherit the value from parent specification. 2

Property "z-index" example:

    <style   type="text/css">
      .pos1 { position: absolute;
              left: 20px;
              top: 20px;}
      .pos2 { position: absolute;
              left: 180px;
              top: 20px;}
      .pos3 { position: absolute;
              left: 20px;
              top: 60px;}
      .pos4 { position: absolute;
              left: 20px;
              top: 120px;}
  <body >
    <p class="pos1" style="z-index: 2"><img
        src="images/ferrari.png" alt="A ferrari image">
    <p class="pos2" style="z-index: 3"><img
        src="images/Trophy.png" alt="A Trophy image">
        The trophy is over the bulp and the ferrari</p>
    <p class="pos3" style="z-index: 1"><img
        src="images/bulb.png" alt="A bulb image">
        The bulp is under the ferrari and the trophy</p>
      This text will be beneath everything.</div>
    <div class="pos4"style="z-index: 4">
      This text will overlay all images.

Javascript access:

// To SET values ([o] is the target object)
[o].style.zIndex="z-index value"
// To GET values you must first get the computed style object
// To get that object in IE or Opera:
var cStyle=[o].currentStyle;
// To get that object in Firefox, Chrome or Safari (w3c-type):
var cStyle=window.getComputedStyle([o],null)
// To GET the property value:;
var value=cStyle.zIndex;
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