1、向中间：background: -webkit-radial-gradient(50% 6%, circle farthest-side, #CAD06C 0, #297141100%);
2、向下：background: linear-gradient(to bottom, #0084c9 0%, #38b9fd 100%);
css样式颜色渐变
原文：http://www.cnblogs.com/may-13/p/7813106.html
