how to deal with google map inside of a hidden div (Updated picture)

I was having the same problem and discovered that when show the div, call google.maps.event.trigger(map, 'resize'); and it appears to resolve the issue for me.

google.maps.event.trigger($("#div_ID")[0], 'resize');

If you don't have variable map available, it should be the first element (unless you did something stupid) in the div that contains GMAP.

Just tested it myself and here's how I approached it. Pretty straight forward, let me know if you need any clarification

HTML

<div id="map_canvas" style="width:700px; height:500px; margin-left:80px;" ></div>
<button onclick="displayMap()">Show Map</button>

CSS

<style type="text/css">
#map_canvas {display:none;}
</style>

Javascript

<script>
function displayMap()
{
    document.getElementById( 'map_canvas' ).style.display = "block";
    initialize();
}
function initialize()
{
    // create the map
    var myOptions = {
        zoom: 14,
        center: new google.maps.LatLng( 0.0, 0.0 ),
        mapTypeId: google.maps.MapTypeId.ROADMAP
    }
    map = new google.maps.Map( document.getElementById( "map_canvas" ),myOptions );
}
</script>