$(function() {
	$('.nav li a')
		.css( {backgroundPosition: "0 0"} )
		.hover(
			function(){
			$(this).stop().animate(
				{backgroundPosition:"(0 -57px)"}, 
				{duration:100})
			},
			function(){
			$(this).stop().animate(
				{backgroundPosition:"(0 0)"}, 
				{duration:250});
			
	});
});