<style type="text/css">
ul {list-style:none;margin:0;padding:0;}
li {float:left;width:100px;margin:0;padding:0;text-align:center;}
li a {display:block;padding:5px 10px;height:100%;color:#FFF;text-decoration:none;border-right:1px solid #FFF;}
li a {background:url(bg2.jpg) repeat 0 0;}
li a:hover, li a:focus, li a:active {background-position:-150px 0;}
#menu a {background:url(bg.jpg) repeat -20px 35px;}

</style>

<script type="text/javascript" src="jquery-1.3.2.min.js"></script>

<script type="text/javascript">

$(function(){
$('#menu a')
.css( {backgroundPosition: "-20px 35px"} )
.mouseover(function(){
$(this).stop().animate({backgroundPosition:"(-20px 94px)"}, {duration:500})
})
.mouseout(function(){
$(this).stop().animate({backgroundPosition:"(40px 35px)"}, {duration:200, complete:function(){
$(this).css({backgroundPosition: "-20px 35px"})
}})
})
});
$(function($) {
$.extend($.fx.step,{
backgroundPosition: function(fx) {
if (fx.state === 0 && typeof fx.end == 'string') {
var start = $.curCSS(fx.elem,'backgroundPosition');
start = toArray(start);
fx.start = [start[0],start[2]];
var end = toArray(fx.end);
fx.end = [end[0],end[2]];
fx.unit = [end[1],end[3]];
}
var nowPosX = [];
nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];

function toArray(strg){
strg = strg.replace(/left|top/g,'0px');
strg = strg.replace(/right|bottom/g,'100%');
strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
}
}
});
});
</script>