Ciao antoedp,

potresti fare accussì
codice:
function controlla(f)
  if (f.value=='si'){ 
    document.getElementById("rag_soc2").style.visibility="visible"; 
    document.getElementById("txt_rag_soc2").style.visibility="visible"; 
  }else{ 
    document.getElementById("rag_soc2").style.visibility="hidden"; 
    document.getElementById("txt_rag_soc2").style.visibility="hidden"; 
  } 
} 
</script> 

<input type="radio" name="NomeRadio" value="si" onClick="controlla(this)"> 
<input type="radio" name="NomeRadio" value="no" onClick="controlla(this)">