I need to reference an external style sheet which is located on the same server but in a different directory to the editor.

I have tried using relative and absolute paths to the style sheet but it doesn't seem to work.  Here is the relative path I have been using:
   
    ../institute/website/styles/style.css

and the absolute path:

    d:\institute\website\styles\style.css

Can you tell me what I am doing wrong .

Thank you