$(document).ready(function(){
				
				var imgArr = new Array( // relative paths of images
					'images/bg01.jpg', 
					'images/bg02.jpg', 
					'images/bg20.jpg', 
					'images/bg04.jpg' 
					);
					
				var preloadArr = new Array();
				var i;
				
				/* preload images */
				for(i=0; i < imgArr.length; i++){
					preloadArr[i] = new Image();
					preloadArr[i].src = imgArr[i];
				}
				
				var currImg = 1;
				var intID = setInterval(changeImg, 7000);
				
				function changeImg(){
					$('#masthead').animate({opacity: 0}, 1000, function(){
						$(this).css('background','url(' + preloadArr[currImg++%preloadArr.length].src +') top center no-repeat');
					}).animate({opacity: 1}, 1000);
				}
 
			});