Col1:
If Firefox and IE can find it, NetSurf should be able to too. There are two possible problems I can think of:
1. The server is not giving it a content type of text/css. If you visit the CSS file directly in NetSurf, you should see a blank page and Page > Info menu option should show "text/css" for Type. e.g. [link] (The CSS file used by the entire NetSurf web site.) If it doesn't show "text/css", the content type is wrong.
2. If you have an @media { ... } block around all the rules in your CSS file, none of the CSS rules will be processed. @media is an currently unsupported.
VinceH:
Yes, that sort of link will be broken if you are working locally and not based in the root directory of the disc. You could put a copy of the CSS file in a temporary skins directory at the root of the disc, while you test the site locally. Or you could copy to a ram disc or something.