960.gs and background-image css

I'm using the 960 grid system to design a site. Problem is, using a stylesheet called style.css and trying to put background images in it they won't display on the site. If i go to the site and write in the styling to the HTML tags they work but I don't want to do that.

Does anyone know how to fix this?

Personally, I would not name your stylesheet "style.css": this can only lead to confusion and possible conflict.

Other than this, the most likely reason it is not working is that the file is not found at the path specified.
Alternatively, the style rules in your file are being over-written by another stylesheet.