以前需要边框长度比容器小一些时，我用div嵌套。后来发现伪类在实现这个效果时很方便，只需要一个div就够了，另外调整padding和margin都不会很麻烦。

<div class="content-block"> 
    <div class="box-container"> <div class="border-top">border top</div> </div> <div class="box-container"> <div class="border-left">border left</div> </div> <div class="box-container"> <div class="border-right">border right</div> </div> <div class="box-container"> <div class="border-bottom">border bottom</div> </div> </div>

.box-container {

    position: relative; width: 90%; color: #777; } .border-top { background: #b4bcbf; padding: 15px; } .border-top:before { content: ''; position: absolute; left: 42%; top: 0; bottom: auto; right: auto; height: 7px; width: 50%; background-color: #8796a9; } .border-left { background: #dfdad6; padding: 15px; } .border-left:before { content: ''; position: absolute; left: 0; top: 6%; bottom: auto; right: auto; height: 52%; width: 5px; background-color: #a89d9e; } .border-right { background: #eee9c4; padding: 15px; } .border-right:after { content: ''; position: absolute; left: auto; top: auto; bottom: 5px; right: 0; height: 52%; width: 5px; background-color: #f39c81; } .border-bottom { background: #bcdc9d; padding: 15px; } .border-bottom:after { content: ''; position: absolute; left: 18px; top: auto; bottom: 0; right: auto; height: 6px; width: 105px; background-color: #32b66b; }

效果如下图：