viewport

<script>
    (function(doc) {
        var viewport = document.getElementById('viewport');
        if ( navigator.userAgent.match(/iPhone/i) || navigator.userAgent.match(/iPod/i)) {
            viewport.setAttribute("content", "initial-scale=0.3");
        } else if ( navigator.userAgent.match(/iPad/i) ) {
            viewport.setAttribute("content", "initial-scale=0.7");
        }
    }(document));
</script>