Given a simple page (source below) that contains an element with a 1px border, it will render like this on Android compared to iOS:
http://f.cl.ly/items/0h2Y0v0u1v1L120m0X0s/Untitled-2.png
As you can see, the Android border does not have a uniform width, sometimes being 1px and sometimes being 2px wide. As far as I've been able to test it, this only occurs on devices with a CSS pixel ratio of 1.5 (including the Android emulator), but not with a pixel ratio of 2 (including iOS). I believe that this problem is caused by subpixel-antialias and/or rounding issues, but I honestly have no idea how I'd go about fixing this.
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title></title>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<style type="text/css">
div {
width: 100px;
text-align: center;
margin-left: 50%;
border: 1px solid magenta;
}
</style>
</head>
<body>
<div>Foobar</div>
</body>
</html>