phranque - 10:22 am on Dec 16, 2009 (gmt 0)
i would look at the path for the href attribute of the link rel="stylesheet" definition.
if the path points to a disk file (for example it starts with C:) or is a relative path i would try specifying a fully qualified absolute path, for example:
<link rel="stylesheet" href="http://example.com/styles/my.css">
then make sure you upload the css file to the right location - in this example, my.css should be uploaded to the styles directory in your document root directory.