Google adsense ads displaying ontop - adsense

Question

I have just added a Google Adsense ad to my page. I have a navbar on my page that is fixed to the top of the screen. The adsense ad is inside a DIV that normally behaves normally and displays under the navbar, but once the ad is displayed the ad displays ontop of the navbar.
Navbar code:
#navbar {
position: fixed;
width: 100%;
height: 66px;
background-color: #1C1C1C;
}
<div id="navbar">
<!-- Orange bar in Navbar-->
<div id="topbar"></div>
<div id="buttons">
<!--Home button-->
<p class="button">- Home</p>
<!--Divider-->
<div class="divider"></div>
<!--Raffles Button-->
<p class="button">Raffles</p>
<!--Divider-->
<div class="divider"></div>
<!--Get tokens Button-->
<p class="dbutton">Get<br>Tokens</p>
<!--Divider-->
<div class="divider"></div>
<!--Token lotto Button-->
<p class="dbutton">Token<br>Lotto</p>
</div>
<div id="signin">
</div>
<div id="profile">
</div>
</div>
Ad DIV:
div#ad300x600 {
margin-left: 50px;
height: 600px;
width: 300px;
background-image: url("miscimg/YUADBLOCK.jpg");
background-size: 0 0;
float: left;
}
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<!-- csgohumblelargeskyscraper -->
<ins class="adsbygoogle"
style="display:inline-block;width:300px;height:600px"
data-ad-client="ca-pub-xxx"
data-ad-slot="xxx"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>
I have tried giving the Ad DIV a z-index: -100; and the Navbar a z-index: 1; but that hasn't helped. How can I make the ad display under the Nav bar. Also something that would be nice instead would be if the ad wouldn't move. But if I give it the position: fixed; tag it pops into the top right corner of the screen and stays there.
http://i.stack.imgur.com/Wts4Q.png
(The grey is the Navbar the white is the Ad)

Answer 1

Seems that if I do an exaggerated amount of z-index like "99999999999" it works fine. Sorry to have posted this and figured out a solution myself.