In ascending order of precedence:
- user agent declarations
- user normal declarations
- author normal declarations
- author important declarations
- user important declarations
CSS spec defines author and user as:
Author. The author specifies style sheets for a source document according to the conventions of the document language. For instance, in HTML, style sheets may be included in the document or linked externally.
User: The user may be able to specify style information for a particular document. For example, the user may specify a file that contains a style sheet or the user agent may provide an interface that generates a user style sheet (or behaves as if it did).
.. but its still not clear to me if I, the developer of the website/app, is the user or the author? Whats the difference between the two?