The linked style sheet is encoded in utf-8 and has an incorrect @charset "iso-8859-1" preceded by a utf-8 BOM. The HTTP server (on purpose) omits the charset parameter. If this text is green, the style sheet is correctly read as utf-8 and the @charset correctly ignored.
[This is not specified in CSS, at least not yet. It assumes the BOM takes precedence over the @charset.]