_footer.sass

footer
  +clearfix
  +media($break-footer)
    padding-bottom: 35px




// Newsletter
#form-newsletter
  +clearfix
  h2
    height: 52px
    background-image: url(../img/section/contact/subscribe.png)
    background-repeat: no-repeat
    background-position: center left
    font-size: 0em
  input[type="email"]
    display: block
    width: calc(100% - 30px)
    margin: 0 auto
    border-bottom: 3px solid $black
    font-size: 1.4em
    +placeholder
      letter-spacing: $letter-spacing-default
      text-transform: uppercase
  input[type="submit"]
    font-size: 1.5em
    text-transform: uppercase
    +transition(color $transition-color linear)
    &:disabled
      color: $grey-lighter

  +media($mobile)
    input[type="submit"]
      float: right
      margin-right: 8px
      padding: 8px

  +media($tablet-min)
    display: block
    position: relative
    float: left
    h2
      float: left
      width: 260px
    input[type="email"]
      float: left
      width: 415px
      height: 40px
      margin-left: 40px
    input[type="submit"]
      position: absolute
      top: 6px
      right: 0


  +media($workstation)
    padding-left: $margin-far-left




// Notice
.become-a-sponsor
  display: block
  font-size: 1.2em
  text-transform: uppercase
  letter-spacing: 0.08em

  +media($mobile)
    margin: 45px 15px 5px 15px
    padding: 4.5px 0
    text-align: center
    border-width: 1px 0
    border-style: solid
    border-color: $grey-lightest

  +media($tablet-min)
    clear: both
    margin: 0 auto
    padding: 45px 0 15px 0
    text-align: center
    font-size: 1.5em

  +media($break-footer)
    float: right
    clear: none
    height: 100%
    margin: 12px 50px 0 0
    padding: 0
    font-size: 1.3em
    &:hover
      text-decoration: underline

index.html

<!-- Footer -->
<footer>

  <!-- Newsletter Subscription -->
  <form id="form-newsletter">
    <h2>Subscribe</h2>
    <input type="email" name="email" placeholder="email" value="" required>
    <input type="submit" name="submit" value="Submit">
  </form>

  <!-- Notice & Sponsor Link -->
  <a class="become-a-sponsor" href="https://creditonline.dealertrack.ca/Web/Default.aspx?Token=629cc512-622e-4894-a25a-20c05e8b289b&amp;Lang=en" target="_blank">Become a Sponsor</a>

</footer>

main.js

(function ($, undefined) { "use strict";

    /*
     * Newsletter Form Submission
     */
     
    var subscribeErrors = [
        "The information provided isn't valid.",
        "You are already subscribed.",
        "An error has occured. Please reload the page and try again."
    ];

    // All possible error messages, indexed by server response
    $('#form-newsletter').submit(function (event) {
        event.preventDefault();

        // Disable button while AJAX is executing
        var btnSubmit = $('#form-newsletter input[type="submit"]'),
            txtEmail = $('#form-newsletter input[type="text"]');
        btnSubmit.attr('disabled', 'disabled');

        // Submit email via POST to subscribe.php
        var xhr = $.ajax({
            type: 'POST',
            url: 'subscribe.php',
            timeout: 7500,
            data: { email: $('#form-newsletter input[type="text"]').val().trim() }
        });

        // Enable out button activating it again
        xhr.always(function () {
            btnSubmit.removeAttr('disabled');
            $('#form-newsletter input[type="text')
        });

        xhr.error(function () {
            alert("There was a problem contacting our server. Please reload the page, and try again.");
        });

        xhr.done(function (response) {
            if (response === '0') {  //Success
                alert('You have successfully subscribed.');
                return true;
            }
            // Error
            if (isNaN(response)) alert("There was a problem subscribing you. Please try again later.");
            else alert(subscribeErrors[parseInt(response) - 1]);
            return false;
        });
    });
    
})(jQuery);