背景颜色设置虚线
width: 50px;
height: 1px;
background: -webkit-linear-gradient(to left,transparent 0%,transparent 50%,#999999 50%,#999999 100%);
background: -o-linear-gradient(to left,transparent 0%,transparent 50%,#999999 50%,#999999 100%);
background: -moz-linear-gradient(to left,transparent 0%,transparent 50%,#999999 50%,#999999 100%);
background: -ms-linear-gradient(to left,transparent 0%,transparent 50%,#999999 50%,#999999 100%);
background: linear-gradient(to left,transparent 0%,transparent 50%,#999999 50%,#999999 100%);
background-size: 5px 1px;background-repeat: repeat-x;
效果：
