iphone 4 safrai fixed

<script type="text/javascript">
    if(navigator.userAgent.indexOf("Safari")>0){
        var onav=document.getElementById("fixnav");
        window.onscroll=function(){
            onav.style.position="absolute";
            onav.style.top=(window.innerHeight+window.scrollY-onav.offsetHeight)+"px";
        }
    }
</script>