I want reset user choice of radiobutton here is my code
form action="mailto:meerovichsergey@gmail.com" method="post" enctype="text/plain">
<fieldset>
<legend>Your opinion</legend>
<input type="radio" name="choice" id="op1" value="All was perfect ,answer to all question." >  All was perfect ,answer to all question.<br/>
<input type="radio" name="choice" id="op2" value="Arcticle is good,but there are a things to improve." >  Arcticle is good,but there are a things to improve.<br/>
<input type="radio" name="choice" id="op3" value="Arcticle doesn't answer my questions" >  Arcticle doesn't answer my questions.<br/>
</fieldset>
</form>
<p align="center"><input type="submit" name="send2" value="Send" onclick="Send()" title="Press to send information" onfocus="Show()" size="10">   <input type="reset" name="reset2" value="Reset" onclick="Res()" title="Press to Reset information" size="10"/></p>
<script type="text/javascript">
function Res()
{
opinion.value="";
document.getElementById("op1").checked=false;
}
</script>
but in some reason it doesn't wotk ,what is wrong with it?