I have followed advice from other topics but can't get it to work. I want to set a background image.

my scss file is custom.css.scss and code is body 

`{ background-image: url("back.png"); }`

`back.png` is located in `app/assets/images`

`custom.css.scss` is located in `app/stylesheets`

i have no problem getting back.png to work through the asset pipeline in my html pages with 

`<%= image_tag "back.png" %>`