Scusate la mia ignoranza ma perchè firefox non mi vede le classi di testo che specifico in un css esterno?

Eppure i codice è semplice

css esterno:

.11_blu_grass {font-family:arial; font-size:11px; color:#054081; font-weight:bold; text-decoration:none}

.11_blu_grass a:link {font-family:arial; font-size:11px; color:#054081; font-weight:bold; text-decoration:none}
.11_blu_grass a:hover {font-family:arial; font-size:11px; color:#cccccc; font-weight:bold; text-decoration:none}
.11_blu_grass a:visited {font-family:arial; font-size:11px; color:#054081; font-weight:bold; text-decoration:none}

Pagina html:

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>prova</title>

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

<body>

<table width="1002" border="0" cellspacing="0" cellpadding="0">
<tr>
<td class="11_blu_grass">ciao</td>
<td>ciao</td>
<td>ciao</td>
</tr>
</table>
</body>
</html>