移动端版本兼容-width自适应

<!--移动端版本兼容 -->
<script type="text/javascript">
var _phoneWidth = parseInt(window.screen.width);
var _phoneScale = _phoneWidth / 640;
var _ua = navigator.userAgent;
if (/Android (\d+\.\d+)/.test(_ua)) {
var version = parseFloat(RegExp.$1);
if (version > 2.3) {
document.write('<meta name="viewport" content="width=640, minimum-scale = ' + _phoneScale + ', maximum-scale = ' + _phoneScale + ', target-densitydpi=device-dpi">');
} else {
document.write('<meta name="viewport" content="width=640, target-densitydpi=device-dpi">');
}
} else {
document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">');
}
</script>
<!--移动端版本兼容 end -->