<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>利用transform实现1px的细线</title>
<style type="text/css">
.line{
position: relative;
margin-top: 20px;
border:none;
}
.line:after{
content: ‘‘;
position: absolute;
top: 0;
left: 0;
border-top: 1px solid red;
-webkit-box-sizing: border-box;
box-sizing: border-box;
width: 100%;
height: 100%;
-webkit-transform: scaleY(0.5);
transform: scaleY(0.5);
-webkit-transform-origin: left top;
transform-origin: left top;
}
.line2{
position: relative;
margin-top: 40px;
border:none;
}
.line2:after{
content: ‘‘;
position: absolute;
top: 0;
left: 0;
border-bottom: 1px solid red;
-webkit-box-sizing: border-box;
box-sizing: border-box;
width: 100%;
height: 100%;
-webkit-transform-origin: left top;
transform-origin: left top;
}
</style>
</head>
<body>
<div class=‘line‘>1</div>
<div class=‘line2‘>1</div>
<script src=‘js/rem.js‘></script>
<script src="http://127.0.0.1:8082/target/target-script-min.js#anonymous"></script>
</body>
</html>
其实是dpi在作怪，现在主流的手机大都是2dpi的，那么一个物理像素会渲染出2px，所以1px的细线就变成了2px，处理方法也很简单。scaleY（0.5）就好。
原文：http://www.cnblogs.com/web-alibaba/p/4841030.html