What Am I Missing? (Form Validator)

hey guys, i have come up with this script after researching on the net but i still cannot get the checkbox to enable the submit button only after the checkbox has been checked...any ideas?

<script type="text/javascript">
/*<![CDATA[*/
function enable_submit(){
var ck = (document.getElementById("notes").checked)? false:true;
          document.getElementById("submit_button").disabled=ck;
}
function valid_email(obj) {
var email_ck = obj.visitormail;
var str = email_ck.value;
var visitor_ck = obj.visitor;
var str2 = visitor_ck.value;
var reg1 = /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/;
var reg2 = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/;
if (str2 == '') {
alert('Please Enter Your Socom Name');
visitor_ck.focus();
return false;
}
if (!reg1.test(str) && reg2.test(str)) {
return true;
}
else {
alert('Please Enter A Valid E-mail Address');
email_ck.focus();
email_ck.select();
return false;
 }
}
/*]]>*/
</script>

<?php
 echo '
 <form method="post" name="JoinRequest" action="sendit.php" onsubmit="return valid_email(this)">';

$ipi = getenv("REMOTE_ADDR");
$httprefi = getenv ("HTTP_REFERER");
$httpagenti = getenv ("HTTP_USER_AGENT");
?>

<input type="hidden" name="ip" value="<?php echo $ipi ?>"/>
<input type="hidden" name="httpref" value="<?php echo $httprefi ?>"/>
<input type="hidden" name="httpagent" value="<?php echo $httpagenti ?>"/>
<br />
<b><font color="#76A5D5" size="2" face="verdana">Socom Name:&nbsp;&nbsp;</font></b>
<input name="visitor" type="text" id="visitor" size="35"/>
<br />
<br />
<b><font color="#76A5D5" size="2" face="verdana">Email Address:</font></b>&nbsp;
<input type="text" name="visitormail" size="35"/>
<br />
<br />
<b><font color="#76A5D5" size="2" face="verdana">Version Trying For:</font></b>&nbsp;
<select name="attn" size="1">
<option value=" Socom1 ">Socom </option>
<option value=" Socom2 ">Socom 2 </option>
<option value=" Socom3 ">Socom 3 </option>
<option value=" Socom4 ">Combined Assult </option>
</select>
<br /><br />
<input type="checkbox" name="notes" value="checkbox" onclick="enable_submit()" />
<font color="#76A5D5" size="1" face="verdana">I Have Read And Agree To Follow The <strong><a href="index.php?view=Rules">Clan Rules</font></a></strong><br />
<br />
<input type="submit" value="Submit" name="submit_button" disabled="disabled">
</form>

Code (markup):

 

You're using getElementId on your enable_submit function but you don't have an ID for the elements you're trying to control. Modify these lines. Take not of the bolded text:

<input type="checkbox" [B]id="notes"[/B] name="notes" value="checkbox" onclick="enable_submit()" />

<input type="submit" value="Submit" [B]id="submit_button"[/B] name="submit_button" disabled="disabled">

Code (markup):

 

cool thanks man