An HTML/Javascript code snippet for Ecwid to show a simple promo message popup on the cart page for orders less than the defined subtotal

ecwid_free_shipping_promo_in_cart.html

<!-- An HTML/Javascript code snippet for Ecwid to show a simple promo message popup on the cart page for orders less than the defined subtotal -->
<script>
if (typeof(Ecwid) == 'object') {
  Ecwid.OnAPILoaded.add(function() {
    var promoMessage = "Orders $99 and up ship free!";
    var minSubtotal = 99;

    var checkSubtotal = function(order) {
      if (order) {
        var subtotal = order.total - order.shipping;
        if (subtotal < minSubtotal) {
          alert(promoMessage);
        }  
      }
    }

    Ecwid.OnPageLoaded.add(function(page) {
      if ('CART' == page.type) {
        Ecwid.Cart.calculateTotal(function(order) {
          checkSubtotal(order);
        });
      }
    });    
  });
}
</script>

The tax also needs to be removed for an accurate subtotal. See this fork for more details.