Edit in JSFiddle

$(function(){
$("body").height($(window).height() + 2000 );　$(window).scroll(function() {
if
($(window).scrollTop() >= ($("body").height() - $(window).height())) {　$(window).scrollTop(1);}
else if
($(window).scrollTop() == 0) {　$(window).scrollTop($("body").height() - $(window).height() - 1);}});
});

body {
height: 2000px;
background: url("http://kachibito.net/sample/endless-roop/bg01.gif") ;
}