Javascript with Ajax refuses to work under firefox and IE9 but doing fine with chrome

[EduCon]

Iam trying to figure out after solving quite a few css problems why a javascript doesnt respond under IE9 and Firefox. The script is quite simplistic still .. no luck !! It is simple an email validation that uses rsv.js by Benjamin Keen and ajax to push data to a php "sign-up" function on a different file. Chrome does this gloriously.. IE no matter what version and firefox, DO NOT.
Any ideas pls pls??

Here is the script that occupies an area between the head:

function sign_up(email) 
        {
        var rules = [];
        rules.push('required,NewsletterEmail,Your Email is necessary for the newsletter!');
        rules.push('valid_email,NewsletterEmail,The Email is Invalid');
        if (rsv.validate(document.getElementById('newsletter'), rules)) {
            $.ajax({
                type: 'POST',
                url: 'scripts/sign-up.php',
                data: 'email='+document.getElementById('NewsletterEmail').value,
                success: function(data){ $('#result').html(data); }
            });
        }
    }

The form that is validated:

<form id="newsletter" name="newsletter">
<input class="email" id="NewsletterEmail" name="NewsletterEmail" value="Email" 
type="text" /><a class="btn" onclick="sign_up(NewsletterEmail.value);">SubmitNow</a>
</form>

IE9 and Firefox describe error as "NewsletterEmai l is not defined" ,,Any ideas????

[EduCon]

Never Mind, found it !!