@import is pointing to the wrong directory.....so it doesn't look like you are using it in your CSS.
I right clicked the element and clicked "Inspect element" in webkit and checked out all the applied styles, position: fixed wasn't one of them meaning that the styles in nav.css weren't getting applied.
That's why I missed it.
Should be @import(nav.css) - it points relative to the CSS file, not the HTML document that the CSS file is linked to.
