摘要：
方案一 高度：在{位置：左：边框左：solid1pxred；宽度：高度：100px；相对；背景色：透明；在{绝对位置：绝对；左：右：边框底部：内容：url（'data:image/svg+xml；
.x { border: solid 1px red; width: 100px; height: 100px; position: relative; background-color: transparent; } .x:before { position: absolute; top: 0px; right: 0; left: 0; bottom: 0; border-bottom: 100px solid red; border-left: 100px solid transparent; content: ""; } .x:after { position: absolute; left: 1px; right: 0; top: 1px; bottom: 0; border-bottom: 99px solid white; border-left: 99px solid transparent; content: ""; } .f { border: solid 1px red; width: 100px; height: 100px; position: relative; background-color: transparent; } .f:before { position: absolute; top: 0px; right: 0; left: 0; bottom: 0; border-bottom: 100px solid red; border-right: 100px solid transparent; content: ""; } .f:after { position: absolute; left: 0; right: 1px; top: 1px; bottom: 0; border-bottom: 99px solid white; border-right: 99px solid transparent; content: ""; }
x 是 斜线， f 是反斜线。
图：
附：CSS 图形：
css3激发想象/css3各种图形 http://www.cnblogs.com/wwcherish/archive/2012/09/18/2690336.html
CSS3机器猫： http://keleyi.com/keleyi/phtml/html5/3.htm
方案二background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="100%"><line x1="0" y1="0" x2="100%" y2="100%" stroke="black" stroke- /></svg>');