lucy24 - 11:42 pm on Nov 3, 2012 (gmt 0)

<link rel="stylesheet" type="text/css" href="styles.css" />

If you look at error logs or something with Live Headers, do you see a request for this file? Have you tried deleting the line and re-typing it manually to make sure no invisible entities sneaked in? Every now and then someone has a problem which turns out to involve a Zero-Width Space or a misplaced BOM.