Precisely positioned body background images. Ain’t gonna ‘appen.

I was just asked how to precisely position a body background image.  Really, it’s not gonna happen.  So… I figured stacking elements is going to be the next best thing.

Basically: Pin a < div > to all 4 walls of the browser window, and then position a containing div where you want, with the background image of your choice. then set that container all behind your actual page content.