You need a max-height
and overflow-y
on the interior elements, and you need to set sizes on the outer elements:
HTML
<div class="outer">
<div class="inner">foo</div>
<div class="inner">bar</div>
<div class="inner">whatever</div>
</div>
CSS
.outer {
border: 2px solid red;
float:left;
top:0;
bottom:0;
position:absolute;
}
.inner {
max-height:100%;
overflow-y:auto;
border: 2px solid blue;
width:30%;
margin-right:2%;
float:left;
}