To set the viewport you should be using this newer method. The way you've done it used to work , but this is now the recommended way:
<!-- set viewport -->
<script>
var meta = document.createElement("meta");
meta.setAttribute('name','viewport');
meta.setAttribute('content','initial-scale='+ (1/window.devicePixelRatio) + ',user-scalable=no');
document.getElementsByTagName('head')[0].appendChild(meta);
</script>