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Stacking with floated blocks

For floated 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;
}

W3cubDocs

Stacking with floated blocks

Example

HTML

CSS

Result

See also