CSS: How to position two elements on top of each other, without specifying a height?

Issue

I have two DIVs that I need to position exactly on top of each other. However, when I do that, the formatting gets all screwed up because the containing DIV acts like there is no height. I think this is the expected behavior with position:absolute but I need to find a way to position these two elements on top of each other and have the container stretch as the content stretches:

The top left edge of .layer2 should be exactly aligned to the top left edge of layer1

<!-- HTML -->
<div class="container_row">
    <div class="layer1">
        Lorem ipsum...
    </div>
    <div class="layer2">
        More lorem ipsum...
    </div>
</div>
<div class="container_row">
    ...same HTML as above. This one should never overlap the .container_row above.
</div>

/* CSS */
.container_row {}

.layer1 {
    position:absolute;
    z-index: 1;
}

.layer2 {
    position:absolute;
    z-index: 2;
}

Solution

First of all, you really should be including the position on absolutely positioned elements or you will come across odd and confusing behavior; you probably want to add top: 0; left: 0 to the CSS for both of your absolutely positioned elements. You'll also want to have position: relative on .container_row if you want the absolutely positioned elements to be positioned with respect to their parent rather than the document's body:

If the element has 'position: absolute', the containing block is established by the nearest ancestor with a 'position' of 'absolute', 'relative' or 'fixed' ...

Your problem is that position: absolute removes elements from the normal flow:

It is removed from the normal flow entirely (it has no impact on later siblings). An absolutely positioned box establishes a new containing block for normal flow children and absolutely (but not fixed) positioned descendants. However, the contents of an absolutely positioned element do not flow around any other boxes.

This means that absolutely positioned elements have no effect whatsoever on their parent element's size and your first <div class="container_row"> will have a height of zero.

So you can't do what you're trying to do with absolutely positioned elements unless you know how tall they're going to be (or, equivalently, you can specify their height). If you can specify the heights then you can put the same heights on the .container_row and everything will line up; you could also put a margin-top on the second .container_row to leave room for the absolutely positioned elements. For example:

http://jsfiddle.net/ambiguous/zVBDc/

Answered By - mu is too short