css实现0.5像素

.border{
     position: relative;
 }

.border:before{
       content: '';
       position: absolute;
       width: 200%;
       height: 200%;
       border: 1px solid red;
       -webkit-transform-origin: 0 0;
       -moz-transform-origin: 0 0;
       -ms-transform-origin: 0 0;
       -o-transform-origin: 0 0;
       transform-origin: 0 0;
       -webkit-transform: scale(0.5, 0.5);
       -ms-transform: scale(0.5, 0.5);
       -o-transform: scale(0.5, 0.5);
       transform: scale(0.5, 0.5);
       -webkit-box-sizing: border-box;
       -moz-box-sizing: border-box;
       box-sizing: border-box;
}