I'am trying to design a website with a background image that should stretch in height and width
accordingly when the browser window is resizing. It is complicated to explain what exact behaviour I would like to achieve, for this reason here is the website that does it perfectly:

<http://de.wix.com/website-template/view/html/709?originUrl=http%3A%2F%2Fde.wix.com%26number-of-page%3D1%26position-in-page%3D4>

I used background-size set to everything possible as well as background-width set to 100%, but
I could not achieve such a behaviour.