I have a centered container div, containing a content div to the left and a nav div to the right. I want the nav div to be fixed, as in not scrolling with content. See image below. Is this doable?

This is indeed possible, use this in your CSS:
.navElement { position: fixed; top: 10px; /*your distance from the top*/ left: 10px; /*your distance from left*/ } Make sure it is the first element in the document flow, right after <body> and it should behave as you described.
position: fixed;. With this you can't use margin centering, (margin: 0 auto;) so you can use the left property to place it as you like. You can use px, em, % or whichever unit you choose as your measurement.