validar "radio boton" en formulario

[bet]

Algo así es lo que precisás?

<pre>
&lt;html&gt;
&lt;head&gt;
&lt;title&gt; Uno solo &lt;/title&gt;

&lt;script language=&quot;JavaScript&quot;&gt;
&lt;!--
function checkForm(frm){
var x = 0;
for (i=0;i&lt;document.forms[0].uno.length;i++){
z = (document.forms[0].uno.checked)?1:0;
x = x + z;
}
if (x &lt; 1){
alert(&quot;Debe seleccionar una opcion&quot;);
return false;
}
}
//--&gt;
&lt;/script&gt;
&lt;/head&gt;

&lt;body bgcolor=&quot;#FFFFFF&quot;&gt;
&lt;form method=&quot;post&quot; action=&quot;pagina2.asp&quot; onsubmit=&quot;return checkForm(this);&quot;&gt;
Pregunta 1:
&lt;input type=&quot;radio&quot; name=&quot;uno&quot; value=&quot;a&quot;&gt;
&lt;input type=&quot;radio&quot; name=&quot;uno&quot; value=&quot;e&quot;&gt;
&lt;input type=&quot;radio&quot; name=&quot;uno&quot; value=&quot;i&quot;&gt;
&lt;input type=&quot;radio&quot; name=&quot;uno&quot; value=&quot;o&quot;&gt;
&lt;input type=&quot;radio&quot; name=&quot;uno&quot; value=&quot;u&quot;&gt;
&lt;input type=&quot;submit&quot;&gt;
&lt;/form&gt;

&lt;/body&gt;
&lt;/html&gt;
</pre>

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