[KidsKilla]

<a href="" class="button" onclick="alert('pressed!');return false;"></a>
+ ксс:
A{display:block; width:100px; height:100px; background:url(static.gif) no-repeat;}
A:hover{background:url(static.gif) no-repeat; background:url(animated.gif) no-repeat;}

и никакого жс