You have a link inside a button which is not allowed and therefore Firefox ignores it.
In html5 you can wrap the anchor around the button but and it should work ok.
However as you really want a link anyway why not just use the anchor alone?
<a class="pull-right btn btn-success" href="basket.php">Checkout<span class="icon-white icon-chevron-right"></span></a>
You may have to teak the margins a little.