http://www.zhangxinxu.com/wordpress/2012/08/window-devicepixelratio/
var iScale = 1; iScale = iScale/window.devicePixelRatio; document.write('<meta name="viewport" content="width=device-width, initial-scale='+iScale+', maximum-scale='+iScale+', user-scalable='+iScale+'"'); var iWidth = document.documentElement.clientWidth/16; document.getElementsByTagName('html')[0].style.fontSize = iWidth + 'px'; document.getElementsByTagName('body')[0].style.fontSize = iWidth + 'px';