The initial appearance of the sidebar can be seen here: https://i.sstatic.net/epGgs.png
When the content fits the original page size, everything looks fine: https://i.sstatic.net/Sfxhb.png
However, once the columns are stacked on top of each other, the sidebar height remains unchanged, resulting in empty space at the bottom: https://i.sstatic.net/5siM4.png
The sidebar is contained within the wrap:
#wrap {width: 100%; height: 100%; position: absolute; top: 0; bottom: 0; left: 0; right: 0}
.sidebar {width: 200px; height: 100%; float: left; background: #65A973; position: relative; bottom: 0px}
Some HTML code here
<div id='wrap'>
<div class='sideBar'>
//content goes here
</div>
<div id='content'>
//content goes here
</div>
<div class='clear'></div>
</div>