<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">
function displayForm(c){
if(c.value == "1"){
document.getElementById("form1").style.visibility='visible';
document.getElementById("form2").style.visibility='hidden';
}
else if(c.value =="2"){
document.getElementById("form1").style.visibility='hidden';
document.getElementById("form2").style.visibility='visible';
}
else{
}
}
</script>
</head>
<body>
<form>
<label>Form 1<input value="1" type="radio" name="formselector" onclick="displayForm(this)"></label>
<label>Form 2<input value="2" type="radio" name="formselector" onclick="displayForm(this)"></label>
</form>
<form style="visibility:hidden" id="form1"><label>Form 1<input type="text"/> </label></form>
<form style="visibility:hidden" id="form2"><label>Form 2<input type="text"/> </label></form>
</body>
</html>