$(document).ready(function()
{
	var check=0;
	var i;
	for(i=0;i<20;i++)
	{
		if($(".a"+i+"").attr("id"))
		{
			check=$(".a"+i+"").attr("id").slice(1,2);
		}
	}
	
	var selected=check*($("#b0").outerWidth());
	var position;
		
	$("#sprite").css({backgroundPosition:''+selected+'px 4px'});
		
	$("#b0,#b1,#b2,#b3,#b4,#b5,#b6,#b7").css({backgroundPosition:'0px 0px'}).mouseover(function()
	{
		position=$(this).attr("id").slice(1,2)*($("#b0").outerWidth())/*width of your list item*/;
		$("#sprite").stop().animate({backgroundPosition:''+position+'px 4px'},{duration:300});
	});
	
	$("#b0,#b1,#b2,#b3,#b4,#b5,#b6,#b7").css({backgroundPosition:'0px 0px'}).mouseout(function()
	{
		$("#sprite").stop().animate({backgroundPosition:''+selected+'px 4px'},{duration:300});
	});
});