图片边框

border-image: url(border.png) 27

默认边框宽度

border-image: url(border.png) 27/27px

指定边框宽27px，默认是拉伸边框图片

border-image: url(border.png) 27/27px repeat

指定边框宽27px，平铺边框图片

border-image: url(border.png) 27/27px round;

指定边框宽27px，round方式平铺边框图片

border-image: url(border.png) 27/27px stretch round;

指定边框宽27px，横向stretch方式覆盖边框图片，纵向round方式平铺图片