resize content div + image on browser resize

What would be the best way to resize a content div to match the brow开发者_如何转开发ser, keeping a white margin around it, whilst also resizing an image contained within it, so that it keeps a good aspect ratio?

this is the effect i am looking to create: http://www.louisvuitton.com/

You would set the margins of the container whether that is the body or another block element container

body {margin:20px;}