a<input name=aaa type=radio checked onclick="changeRadio()"><textarea name=ddd></textarea><br>b<input name=aaa type=radio onclick="changeRadio()">
<script>
function changeRadio()
{
if(aaa[0].checked)
{
ddd.style.display="";
ddd.disabled=false;
}else
{
ddd.style.display="none";
ddd.disabled=true;
}}
</script>
<script>
function changeRadio()
{
if(aaa[0].checked)
{
ddd.style.display="";
ddd.disabled=false;
}else
{
ddd.style.display="none";
ddd.disabled=true;
}}
</script>
<input type="radio" name="a" onclick="document.all.T.style.display='none'">b
<BR>
<textarea id="T" style="display:none"></textarea>
<input type = radio name = r1 onclick ="div1.style.display = 'none'">
<div id= div1><textarea ></textarea></div>