In overall_header.html, I used </div> tag of search codes
Code
<div class="forabg">
<div class="inner">
<span class="corners-top"><span></span></span>
<ul class="topiclist">
<li class="header"><dl><dt><script type="text/javascript"><!--
google_ad_client = "pub-your adsense pub number";
/* 728x90, created 5/26/08 */
google_ad_slot = "4245940906";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script></dt></dl></li>
</ul>
<ul class="topiclist forums">
<li><dl>
<dd class="posts_portal">
</dd>
</dl></li>
</ul>
<span class="corners-bottom"><span></span></span>
</div>
</div>
here is example from my another forum. You can see a banner ad of this site in top bar of my another forum. Google ad was there before but i replaced it now with my own advertisement.
You can add your ad codes anywhere. see carefully my ads codes for your reference. The ad codes have also been tested after <div class="forabg"> and it worked. You can put above codes anywhere you desire it to appaear in your phpbb 3 prosilver theme.
I think it will work in other themes too.
