Children element with height: 100% getting pushed by siblings

Question 1

You could float the h1 element. It would work no matter what height it is, and the content of the stretch element will be pushed below it. But I'm not entirely sure if this is what you are looking for.

EDIT: I'm not certain what kind of browser support you're looking for, but you could also set the display to table on .parent and then have .stretch inherit the height. Then you can nest the column divs inside of .stretch and float them.

Updated: http://jsbin.com/oluyin/2/edit

HTML

<div class="parent">
    <h1>Element taking space</h1>
    <div class="stretch">
        <div class="col">Not much content, but needs to be stretched to the end.</div>
        <div class="col">Not much content, but needs to be stretched to the end.</div>
    </div>
</div>

CSS

.parent {
    display: table;
}

.stretch {
    height: inherit;
}

.col {
    float: left;
    width: 50%;
}

Question 2

In the time since this question was asked and answered, a better way to achieve this has come into existence: flex-box.

Just set the parent's display to "flex" and flex-direction to "column", and set the "stretchy" child's height to "inherit". The child will inherit a height of however many pixels are left over to fill up its parent.

In the following example, lines marked /* important */ are part of the actual solution; the rest of the CSS is just to make it visually easier to understand.

.parent {
  display: flex; /* important */
  flex-direction: column; /* important */
  height: 150px;
  border: 6px solid green;
}

h1 {
  background: blue;
  margin: 0px;
  height: 90px
}

.stretch {
  background: red;
  height: inherit; /* important */
}

<div class="parent">
    <h1>Element taking space</h1>
    <div class="stretch">
        Not much content, but needs to be stretched to the end.
    </div>
</div>

Question 3

If you know the height of your H1 you can do this to fill out the child:

.parent {

  background-color: #eee;
  border: 1px solid black;
  width: 300px;
  height: 600px;
  position:relative;

}

h1 { Height: 100px; }

.stretch
{
  background-color:#dddddd;
  position: absolute;
  left: 0;
  width: 100%;
  top: 100px;
  bottom: 0;
}

Example: http://jsbin.com/apocuh/1/edit

If you don't know the height of H1, I'm afraid you will probably need to use JavaScript or thgaskell's method.

Take a look at this post for more information, and an example with JS: CSS: height- fill out rest of div?

Question 4

Maybe using display:table properties fits your needs ?

Edit: This answer actually looks like thgaskell's one, but instead of using floats I use table-row and table-cell display, and it seems to achieve what you are looking for.

Here is the jsfiddle : http://jsbin.com/ebojok/17/edit

.parent {

  background-color: #eee;
  border: 1px solid black;
  width: 600px;
  height: 600px;
  display:table;

}

h1{
  display:table-row;
  width:100%;
}


.stretch{

  vertical-align:top;
  display:table-cell;
  height:100%;
  background-color: #ddd;

}

Question 5

HTML

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>JS Bin</title>
</head>
<body>
  <div class="parent">
    <h1>Element taking space</h1>
    <div class="stretch">Not much content, but needs to be stretched to the end.</div>
  </div>
</body>
</html>

CSS

.parent {

  background-color: #eee;
  border: 1px solid black;
  width: 300px;
  height: 600px;
  position:relative;

}

.stretch {

  background-color: #ddd;
  height: 100%;
  position: absolute;  
  top: 0;
}

http://jsbin.com/amesox/1/edit

This will cover your h1 element as the .stretched goes over it. You could get around this by using z-index: 1; on your h1 element, but I'd advise against it if you want text in your .stretched element.

You need position:relative; on your parent div to give position: absolute something to 'hook on' to. absolute positioned elements, ignore other elements and are placed on top of them unless their z-index is higher or they are its children.