a me questo codice funziona
codice:
<html>
<body>
<form name="my_form_n">
<table  align="center" width="40%" border="1">
    <tr>
    <td width="2%"><input type="radio" name="file_newsletter" value="file.html"></td>
    <td><a href="contenuti_news/file.html" title="Visualizza" target="_blank"><font 

color="#011F75">file.html</font></a></td>
    </tr>
</table>


<p align="center"><input type="button" value="Inserisci"
onClick="alert(document.my_form_n.file_newsletter.value)"></p>
</form>
</body>
</html>