So gaiour is right, but if you're looking for a full height item that doesn't scroll with the content, but is actually the height of the container, here's the fix. Have a parent with a height that causes overflow, a content container that has a 100% height and overflow: scroll, and a sibling then can be positioned according to the parent size, not the scroll element size. Here is the fiddle: http://jsfiddle.net/M5cTN/196/
and the relevant code:
html:
<div class="container">
<div class="inner">
Lorem ipsum ...
</div>
<div class="full-height"></div>
</div>
css:
.container{
height: 256px;
position: relative;
}
.inner{
height: 100%;
overflow: scroll;
}
.full-height{
position: absolute;
left: 0;
width: 20%;
top: 0;
height: 100%;
}