伪类共用样式缩写形式

.top::before , .top::after{
    content: "";
    position: absolute;
    width: 200%;
    left: 0;
    height: 0;
    border-top: 1px solid #cccccc;
    transform-origin: left top;
    -webkit-transform-origin: left top;
    -o-transform-origin: left top;
    -moz-transform-origin: left top;
    transform: scale3d(0.5, 0.5, 0.5);
    -webkit-transform: scale3d(0.5, 0.5, 0.5); /* Chrome, Safari */
    -o-transform: scale3d(0.5, 0.5, 0.5); /* Opera */
    -moz-transform: scale3d(0.5, 0.5, 0.5); /* firefox*/
}

.top::after{
    border-bottom: 1px solid #cccccc;
}