Are you missing a - from your class name? There should be two after page, like this: .page--full_bg__background. If it still doesn’t work after that, I would recommend looking in your browser’s developer tools to see if the image definitely exists. Remember that URLs in a CSS file are relative to the CSS file itself, not the page it is included in. So maybe it should be more like background: url('/img/Backg.png');?