codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD>
<TITLE></TITLE>

<SCRIPT language="JAVASCRIPT" type="text/JAVASCRIPT">
function send() {
var name = document.newsletter.name.value;
var address = document.newsletter.address.value;
var select = document.newsletter.select[0];
var select_1 = document.newsletter.select[1];
var format = (document.newsletter.select[0].checked)? "HTML" : "TXT";
if ((name == "") || (name == "undefined")) {
alert("NAME NOT FOUND");
document.newsletter.name.focus();
}
else if ((address == "") || (address == "undefined")) {
alert("ELECTRONIC MAIL ADDRESS NOT FOUND");
document.newsletter.address.focus();
}else if (address.lastIndexOf("@")==-1 && address.lastIndexOf(".")==-1){
alert("ELECTRONIC MAIL IS NOT VALID");
document.newsletter.address.focus();
}
else if ((!select.checked) && (!select_1.checked)) {
alert("SELECT NOT FOUND");
document.getElementById('td_select').style.background='red'
document.getElementById('td_select_1').style.background='red'
}
else { location.href = "mailto:" + address+ "?subject=" + "LA SQUADRA NEWS LETTER" + "&body=" + "NAME " + name + " " + "ELECTRONIC MAIL ADDRESS " + address + " " + "SELECT " + format; }
}
</SCRIPT>

</HEAD>
<BODY bgcolor="#000097">

<FORM name="newsletter">
<TABLE align="center" width="50%" border="1" bgcolor="#CCCCCC" cellpadding="5">
<TR align="center" bgcolor="#FFFBF0">
  <TD colspan="3" align="center"><font size="4" face="Arial, Helvetica, sans-serif">News Letter </font></TD>
  </TR>
<TR align="center">
<TD align="center" width="36%"><DIV align="center"><FONT face="Arial" size="2" color="#000000">NAME</FONT></DIV></TD>
<TD colspan="2" align="center">
<DIV align="center"><INPUT type="text" name="name" style="font-family:Verdana;font-size:10px;color:#000000;" value=""></DIV>
</TD>
</TR>
<TR align="center" width="25%">
<TD><DIV align="center"><FONT face="Arial" size="2" color="#000000">ELECTRONIC MAIL ADDRESS</FONT></DIV></TD>
<TD colspan="2" align="center">
<DIV align="center"><INPUT type="text" name="address" style="font-family:Verdana; font-size:10px; color:#000000;" value=""></DIV>
</TD>
</TR>
<TR align="center">
<TD align="center" width="36%"><DIV align="center"><FONT face="Arial" size="2" color="#000000">Format</FONT></DIV></TD>
<TD id="td_select" align="center" width="33%"><INPUT name="select" type="radio" onClick="document.getElementById('td_select').style.background='';document.getElementById('td_select_1').style.background=''
" value="HTML">
  <font size="2" face="Arial, Helvetica, sans-serif">  HTML</font></TD>
<TD id="td_select_1" align="center" width="31%"><input type="radio" onClick="document.getElementById('td_select').style.background='';document.getElementById('td_select_1').style.background=''" name="select" value="TXT">
  <font face="Arial" size="2" color="#000000">TXT</font></TD>
</TR>
<TR align="center" bgcolor="#FFFFFF">
<TD align="center" colspan="3">
<DIV align="center">[img]../immagini/reset.gif[/img] 
    [img]../immagini/send.gif[/img]</DIV>
</TD>
</TR>
</TABLE>
</FORM>

</BODY>
</HTML>
La pagina funziona perfettamente, ti consiglio di copiare e incollare tutto cosi da non perdere niente.

PS unisci la parola javascript la separa il form di html.