手机端 一个像素线解决方案

 background-repeat: repeat-x;
    -webkit-background-size: 100% 1px;
    background-position: left bottom;
    background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0.5, transparent), color-stop(0.5, #e4e4e4), to(#e4e4e4));