navigationControl, mapTypeControl and scaleControl go behind the map

I am going to make an app in which there is a section to display a marked location on Google Maps. Everything works well but Google Map tools like navigationControl, mapTypeControl and scaleControl become hidden in some devices like Samsung Galaxy Tab 10.1 ( they seem to go behind the map ). Even I've changed their value to true but they are still hidden in some devices.

Here is what I've made:

       <--! The HTML -->
       <article class="container">
       .
       .
       .
       ...( some tags go here )

            <section class="span12">
                <div id="mapDiv"> </div>
            </section>

       </article>  

/*The Javascript*/
<script src="http://maps.google.com/maps/api/js?sensor=false"></script>

<script type="text/javascript">

 function initialize() {
     var position = new google.maps.LatLng(38.89655520572012, -77.03372955322266); 
     var myOptions = {
     zoom: 15,
     center: position,
     mapTypeId: google.maps.MapTypeId.ROADMAP,
     };
     var map = new google.maps.Map(
     document.getElementById("mapDiv"), myOptions);

     var marker = new google.maps.Marker({
     position: position,
     map: map,
     title:"We are here.",
     }); 
     }
</script>

Does anybody know why they become hidden?!

Any help is appreciated.