Adding a sidebar (Asterix theme)

I've been trying to add a sidebar over at http://grawlix.bitsfair.com/ but my attempt does not look very good atm hahh.

I added the html for the sidebar in page.comic.php, right after the code for the blogpost. (I've tried plugging it in a dozen different spots, but nothing made things look as they should.)

My CSS for the whole thing is:

.sidebar {
float: right;
position: relative;
width: 160px;
}

.secondary__blog {
float: left;
position: absolute;
width: 100%;
padding-right: 160px;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}

Which I got from here: http://stackoverflow.com/questions/18775612/three-column-design-dynamic-width-left-right-side-and-static-witdh-in-the-mid

How do I stop the footer from climbing on top of the blogpost?