function preloadImages(imgs){
	
	var picArr = [];
	
		for (i = 0; i<imgs.length; i++){
			
				picArr[i]= new Image(100,100); 
				picArr[i].src=imgs[i]; 

			
			}
	
	}
	
	preloadImages([
		'images/nav-act1.png', 
		'images/nav-act2.png', 
		'images/nav-act3.png', 
		'images/nav-act4.png', 
		'images/nav-act5.png', 
		'images/nav-act6.png',
		'images/nav-act7.png',
		'images/nav-act8.png'
	]);