Hello, I'm hoping someone can please help me.I downloaded a PHP form mailer script from Dagon Design (click to download script) and everything works great. I recommend this script to anyone looking for an advanced mailer form. I am having some trouble creating an "onclick" function for the radio and checkbox buttons. I have tried to add in this code but have had no success.

Code:
<input id="first" name="first" onclick="document.getElementById('firstfile').style.display='block'; document.getElementById('secondfile').style.display='none';return false;" checked="checked" />
<input id="second" name="second" onclick="document.getElementById('secondfile').style.display='block'; document.getElementById('firstfile').style.display='none';return false;" />
(...)
<div id="firstfile" style="display:block;">
    <?php include('includes/myfirstfile.php"); ?>
</div>

<div id="secondfile" style="display:none;">
    <?php include('includes/mysecondfile.php"); ?>
</div>
Can anyone Please help me? Thank You!