html - CSS transition fails for background-image url

Question

Following examples found on Fade Effect on Link Hover?

I made this: http://jsfiddle.net/felipelalli/ns9d1vug/

<div class="fade"/>

.fade {
-o-transition: 0.3s;
-moz-transition: 0.3s;
-khtml-transition: 0.3s;
-webkit-transition: 0.3s;
-ms-transition: 0.3s;
transition: 0.3s;

 width:128px;height:128px;
background:url('http://nuclearpixel.com/content/icons/2010-02-09_stellar_icons_from_space_from_2005/earth_128.png')
}

.fade:hover {
color: #b50000;
    width:128px;height:128px;
 background:url('http://upload.wikimedia.org/wikipedia/commons/b/b2/Crystal_128_babelfish.png')
}

Why it works fine in Chrome but not Firefox?

Answer 1

It isn't working in FF, because Firefox does not support transitioning a background image, only background-color. If you want to transition a background image, use two separate <div>:

.fade div {
-o-transition: 0.3s;
-moz-transition: 0.3s;
-khtml-transition: 0.3s;
-webkit-transition: 0.3s;
-ms-transition: 0.3s;
transition: 0.3s;
 width:128px;
  height:128px;
  position:absolute;
  top:0;
  left:0;
}
.fade{
  position:relative;
  width:128px;
  height:128px;
  }
.backone{
  z-index:1;
  background:url('http://nuclearpixel.com/content/icons/2010-02-09_stellar_icons_from_space_from_2005/earth_128.png');
  }
.backtwo{
background:url('http://upload.wikimedia.org/wikipedia/commons/b/b2/Crystal_128_babelfish.png');
  opacity:0;
z-index:5;
}
.fade:hover .backtwo{
opacity:1;
}
.fade:hover .backone{
opacity:0;
}

<div class="fade">
<div class="backone"></div>
<div class="backtwo"></div>
</div>