移动设备页面自适应

;(function(){
    var w = parseInt(window.screen.width),
        s = w/640,
        u = navigator.userAgent.toLowerCase(),
        m = '<meta name="viewport" content="width=640,';
    if (/android (d+.d+)/.test(u)){
        if(parseFloat(RegExp.$1)>2.3) m += 'minimum-scale='+s+',maximum-scale='+s+',';
    }else{
        m += 'user-scalable=no,';
    }
    m += 'target-densitydpi=device-dpi">';
    document.write(m);
}());