滚动背景特效

说明：  这些代码可以实现网页背景的动态变换，使整个网页的效果特别富于变化，非常生动，我个人在制作中经常使用这种方法。
(these codes can achieve dynamic website transform the background, the effect of the whole page special dividend changes, very vividly, I personally made frequent use of this method.)