I have created a basic Routing-system in PHP. The url is split into an array, so that i can decide what to show depending on the URL (ex: www.domain.com/page/option/param).
With most rewriting of "fake" or friendly URL's, you need to specify the location of the stylesheet either using absolute path or using the base tag in the head section.
e.g.
//The CSS file above will load from http://example.com/css/style.css
OR
You can add a back slash before the path in the link tag so that it starts at the root directory.