<div class="page">
<div class="container">
<div class="upper">
content that can dynamically change
<div>normally</div>
<div>this</div>
</div>
<div class="lower">
this should fill the remaining space and scroll if it has:
<div>more content1</div>
<div>more content2</div>
<div>more content3</div>
<div>more content4</div>
<div>more content5</div>
</div>
</div>
<div class="container">
<div class="upper">
content that can dynamically change
<div>but sometimes</div>
<div>it</div>
<div>can</div>
<div>grow</div>
</div>
<div class="lower">
this should fill the remaining space and scroll if it has:
<div>more content1</div>
<div>more content2</div>
<div>more content3</div>
<div>more content4</div>
<div>more content5</div>
</div>
</div>
</div>