$(document).ready(function(){

	$(".mainNav li").hover(
		function() { 
			$(this).children('ul').fadeIn("fast");
			$(this).children('a').css("background-position","left bottom");
		},
		function() { 
			$(this).children('ul').fadeOut("fast");
			$(this).children('a').css("background-position","left top");
		}
	);
	
});