prova così:

<style type="text/css">
A.nounder {
text-decoration: none;
}
</style>

oppure

<style type="text/css">
A:link.nounder {
text-decoration: none;
}
A:visited {
text-decoration: none;
}
A:active {
text-decoration: none;
}
</style>

ciao :metallica