Why is my CSS :hover @keyframes animation not working?

Question

I am a newbie. Why is this code not working? I want to make the bird fly.

My html:

<img src="http://dl.dropboxusercontent.com/u/105046436/tw.png" />
<br>
<div class="twitter-bird"></div>

My CSS:

.twitter-bird {
    background-image: url(http://dl.dropboxusercontent.com/u/105046436/tw.png);
    display: inline-block;
    height: 38px;
    width: 37.5px;
}

.twitter-bird:hover {
    animation: fly 0.2s steps(3) 0 infinite;
}

@keyframes fly {
    from { background-position: 0 0; }
    to { background-position: -112.5px 0; }
}

JSFiddle : http://jsfiddle.net/6qHMG/

What I want:

I want to change the background position of the image.

What happens:

Image position does not change on hover.

EDIT: I think the background image position does not change properly. The background-position doesn't seem to change. How do I set background-position: in @keyframes fly ?

Solution

here it is:

u have to add vendor prefixes

.twitter-bird {
    height: 38px;
    width: 37.5px;
    background-image: url("http://dl.dropboxusercontent.com/u/105046436/tw.png");
}

.twitter-bird:hover { 
    -webkit-animation: fly .4s steps(3) infinite;
       -moz-animation: fly .4s steps(3) infinite;
        -ms-animation: fly .4s steps(3) infinite;
         -o-animation: fly .4s steps(3) infinite;
            animation: fly .4s steps(3) infinite;
}

@-webkit-keyframes fly {
   from { background-position:    0px; }
     to { background-position: -112.5px; }
}

@-moz-keyframes fly {
   from { background-position:    0px; }
     to { background-position: -112.5px; }
}

@-ms-keyframes fly {
   from { background-position:    0px; }
     to { background-position: -112.5px; }
}

@-o-keyframes fly {
   from { background-position:    0px; }
     to { background-position: -112.5px; }
}

@keyframes fly {
   from { background-position:    0px; }
     to { background-position: -112.5px; }
}

fiddle: http://jsfiddle.net/6qHMG/4/

Comments

[Farshid Saberi]

Vendor prefix is required for chrome, safari and opera. ie and firefox, support standard keyword.