Once form validated, I need to have a redirect page

CMS & WordPress
1

I have a script that already validates the person’s entry to sign up for a newsletter, but I would like the submit button to redirect to a page or popup notifying the user to check the e-mail they entered. How do I go about doing this only in the case of the user entering something into the field???

(I already know how to do a basic onClick stuff, but that doesn’t distinguish whether the user entered anything in the field.)

Here is the site so that you can have a look at what the form looks like: http://s94254.gridserver.com/

Thanks in advance for any help!! (Please make it as simple as you can because I am not advanced at this stuff.)

Here is my code to make it easier to understand:

<!-- Begin MailChimp Signup Form -->
<script type="text/javascript">// <![CDATA[
// delete this script tag and use a "div.mce_inline_error{ XXX !important}" selector
// or fill this in and it will be inlined when errors are generated
var mc_custom_error_style = '';
// ]]></script>
<script src="http://homesteadcompany.us1.list-manage.com/js/jquery-1.2.6.min.js" type="text/javascript"></script>
 <script src="http://homesteadcompany.us1.list-manage.com/js/jquery.validate.js" type="text/javascript"></script>
<script src="http://homesteadcompany.us1.list-manage.com/js/jquery.form.js" type="text/javascript"></script>
 <script src="http://homesteadcompany.us1.list-manage.com/subscribe/xs-js?u=b6c011d5468429c66dca5617b&amp;id=a05121dd7e" type="text/javascript"></script>

<div align="center" id="mc_embed_signup">
<form id="mc-embedded-subscribe-form" class="validate" action="http://homesteadcompany.us1.list-manage.com/subscribe/post?u=b6c011d5468429c66dca5617b&amp;id=a05121dd7e" method="post">
<fieldset>
 <legend></legend>

<input id="mce-EMAIL" class="required email" name="EMAIL" type="text" />
</div>
<div class="mc-field-group">
<label for="mce-EMAIL">
<strong></strong>
</label>

<div align="center" style="padding:5px;">
<input id="mc-embedded-subscribe" class="btn" name="subscribe" type="submit"  value="Subscribe"  style="background-color: #F5D991; color: #000000; font-weight: bold; font-family: Arial; font-size: 15px; border-style: solid; border-width: 1; border-color: #FFFFFF "/ >
</div>
</fieldset>
</form>
</div>
<!--End mc_embed_signup-->