Is there a way to extend the height of my sidebar until it reaches the footer without putting any content. It will look awkward if it has white space at the bottom.
There are several ways of doing that. Using a background image as a faux column and display:table-cell are the basis of two such methods, there are others. If you can give us a link to your site so we can see the code you are using to construct your page, we can make better recommendations.