Stacking floating elements
For floating elements, the stacking order is a bit different. Floating elements are placed between non-positioned elements and positioned elements:
- The background and borders of the root element.
- Descendant non-positioned elements, in order of appearance in the HTML.
- Floating elements.
- Descendant positioned elements, in order of appearance in the HTML.
See types of positioning for an explanation of positioned and non-positioned elements.
Note: If an opacity
value is applied to a non-positioned element (i.e., DIV #4 in the example below), something strange happens: the background and border of that block pop up above the floating blocks and the positioned blocks. This is due to a peculiar part of the specification: applying an opacity
value creates a new stacking context (see What No One Told You About Z-Index).
Example
You can see in this example that the background and border of the non-positioned element (DIV #4) is completely unaffected by floating elements, but the content is affected. This happens according to standard float behavior which can be shown with a rule added to the above list:
- The background and borders of the root element.
- Descendant non-positioned elements, in order of appearance in the HTML.
- Floating elements.
- Descendant non-positioned inline elements.
- Descendant positioned elements, in order of appearance in the HTML.
HTML
<div id="abs1"><strong>DIV #1</strong><br />position: absolute;</div>
<div id="flo1"><strong>DIV #2</strong><br />float: left;</div>
<div id="flo2"><strong>DIV #3</strong><br />float: right;</div>
<br />
<div id="sta1"><strong>DIV #4</strong><br />no positioning</div>
<div id="abs2"><strong>DIV #5</strong><br />position: absolute;</div>
<div id="rel1"><strong>DIV #6</strong><br />position: relative;</div>
CSS
div {
padding: 10px;
text-align: center;
}
strong {
font-family: sans-serif;
}
#abs1 {
position: absolute;
width: 150px;
height: 200px;
top: 10px;
right: 140px;
border: 1px dashed #900;
background-color: #fdd;
}
#sta1 {
height: 100px;
border: 1px dashed #996;
background-color: #ffc;
margin: 0px 10px 0px 10px;
text-align: left;
}
#flo1 {
margin: 0px 10px 0px 20px;
float: left;
width: 150px;
height: 200px;
border: 1px dashed #090;
background-color: #cfc;
}
#flo2 {
margin: 0px 20px 0px 10px;
float: right;
width: 150px;
height: 200px;
border: 1px dashed #090;
background-color: #cfc;
}
#abs2 {
position: absolute;
width: 150px;
height: 100px;
top: 80px;
left: 100px;
border: 1px dashed #990;
background-color: #fdd;
}
#rel1 {
position: relative;
border: 1px dashed #996;
background-color: #cff;
margin: 0px 10px 0px 10px;
text-align: left;
}
Result
See also
- Stacking without the z-index property: The stacking rules that apply when
z-index
is not used. - Using z-index: How to use
z-index
to change default stacking. - 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