span:hover isn't working in Firefox but works in Chrome

Question

I have a piece of code that I doesn't work in Firefox. The .icon image does not change when the button is hovered. It works perfectly in Chrome.

button.add-to-cart-button .button-left .icon {
  display: block;
  position: absolute;
  left: 0;/*RW 6px; */
  top: 0;/*RW  6px; */
  width: 35px;/*RW 21px; */
  height: 31px;/*RW 19px; */
  background: url(http://client4.bostonwebco.com/skin/ideal_responsive/images/custom/add_to_cart.gif) 50% 50% no-repeat;
}
button.add-to-cart-button .button-left {
  display: block;
  text-indent: -5000px;
  overflow: hidden;
  padding-left: 0px !important;/*RW  2px  */
  width: 35px !important;/*RW  30px  */
  position: relative;
  font-size: 11px;
  text-align: center;
  border: 0px;
  height: 31px;
  margin: 0px;
}
button.add-to-cart-button:hover span.button-left:hover span.icon:hover {
  background: url("http://client4.bostonwebco.com/skin/ideal_responsive/images/custom/add_to_cart-over.gif") 50% 50% no-repeat !important;
  display: block;
  border: none;
}

<div class="buttons-row">
  <button class="button main-button add-to-cart-button" type="submit" title="Add to cart">
    <span class="button-right">
      <span class="button-left">
        <span class="lbl" id="lbl_add_to_cart" onmouseover="javascript: lmo(this, event);">Add to cart</span>
        <span class="icon"></span>
      </span>
    </span>
  </button>
</div>

JS Fiddle: http://jsfiddle.net/dKcdK/14/

Answer 1

Your issue is that Firefox does not respond to the :hover selector of an element if it is a child of a button. See https://bugzilla.mozilla.org/show_bug.cgi?id=843003.

You can simplify your CSS by attaching :hover to the button instead:

button.add-to-cart-button .button-left .icon {
  display: block;
  position: absolute;
  left: 0;/*RW 6px; */
  top: 0;/*RW  6px; */
  width: 35px;/*RW 21px; */
  height: 31px;/*RW 19px; */
  background: url(http://client4.bostonwebco.com/skin/ideal_responsive/images/custom/add_to_cart.gif) 50% 50% no-repeat;
}
button.add-to-cart-button .button-left {
  display: block;
  text-indent: -5000px;
  overflow: hidden;
  padding-left: 0px !important;/*RW  2px  */
  width: 35px !important;/*RW  30px  */
  position: relative;
  font-size: 11px;
  text-align: center;
  border: 0px;
  height: 31px;
  margin: 0px;
}
.add-to-cart-button:hover .icon {
  background: url("http://client4.bostonwebco.com/skin/ideal_responsive/images/custom/add_to_cart-over.gif") 50% 50% no-repeat !important;
  display: block;
  border: none;
}

<div class="buttons-row">
  <button class="button main-button add-to-cart-button" type="submit" title="Add to cart">
    <span class="button-right">
      <span class="button-left">
        <span class="lbl" id="lbl_add_to_cart">Add to cart</span>
        <span class="icon"></span>
      </span>
    </span>
  </button>
</div>