//NAVIGATION SYSTEM
var navigate = function() {
			//for the one currently selected item, set it's BG position to show the item
		$('nav ul li.selected').css({'backgroundPosition' : '0 0'});
		
		//hover effect, using backgroundposition.js, pull the image down on mouseover, restore when mouseout
		$('nav ul li').not('.selected').hover(function() {		
			$(this).stop()
			.animate({
				backgroundPosition: '0 0'
			}, 600);
		}, function() {
			$(this).stop()
			.animate({
				backgroundPosition: '0 -100px'
			}, 600);	
		});
	};