Local style sheets will need '.css' on the end.
--- a/publish.xsl	Thu May 10 10:18:07 2012 +0200
+++ b/publish.xsl	Wed May 16 20:04:46 2012 +1000
@@ -169,7 +169,7 @@
         </title>
         <xsl:apply-templates select='head/*[not(self::link) and not(self::meta) and not(self::title)]'/>
         <xsl:apply-templates select='head/link[not(@rel="stylesheet" and contains(@href, "StyleSheets/TR") or @media="print")]'/>
-        <link rel='stylesheet' href='{if ($local-style-sheets) then "style/" else "http://www.w3.org/StyleSheets/TR/"}W3C-{$maturity-short}' type='text/css' media='screen'/>
+        <link rel='stylesheet' href='{if ($local-style-sheets) then "style/" else "http://www.w3.org/StyleSheets/TR/"}W3C-{$maturity-short}{if ($local-style-sheets) then ".css" else ""}' type='text/css' media='screen'/>
       </head>
       <body>
         <xsl:attribute name='class'>