Getting footer to stay on bottom

Does anyone know how I can get my footer to stay on the bottom of the window? It currently floats up to whatever is above it.

It’s not all that straightforward, actually, but here’s a tutorial on how to do it:

On my large screen, that would mean your footer is a long way down below the other content. Are you sure you really want that?

Well what I would like to do is have a auto adjusting, centered, full size background image between the header and footer. Then overlay text on the left side for my about me page.