$(function(){  
			$('#navigation li a').append('<span class="hover"></span>');  
            // span whose opacity will animate when mouse hovers.  
   
            $('#navigation li a').hover(  
            	function() {  
              		$('.hover', this).stop().animate({  
             			'opacity': 1  
             		}, 700,'easeOutSine')  
             	},  
             	function() {  
            		$('.hover', this).stop().animate({  
             			'opacity': 0  
             	}, 700, 'easeOutQuad')  
   			})  
});