说明：border-width: top right bottom left;(四个值)border-width: top=bottom left=right;（两个值）border-width: top left=right bottom;（三个值）border-width: top=right=bottom=left;（一个值）border-top-widthborder-right-widthborder-bottom-widthborder-left-widthborder-color（颜色），border-style(形状)与border-width一样有四个方向的值
