网页上的下雨特效，需要把网页的背景色设成其它颜色，否则看不清，因为雨是白色的。在JS代码中，雨滴的大小和数量可以自定义，之前发过下雨的效果。

-Rain effects on a Web page, you need to set the background color of the page into other colors, otherwise not see, because the rain is white. In the JS code, size and number of raindrops can customize, sent a rain effect before.