Here's my google adsense banner code.
Code:
<center><script type="text/javascript"><!--
google_ad_client = "Your pub id here*********";
/* After Forum banner */
google_ad_slot = "*******";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script></center>
Alternately you can link to an image of a particular size. also
Here's my site sponsor ad
Code:
</script><center>
<p>Site Sponsor:</p>
<a href="http://whitey10tc.webs.com/KC%20PHONE%20AND%20FLASH.htm" target="_blank"> <img src="http://whitey10tc.webs.com/MySpaceGens_7389676365.gif"> </a>
</center></script>
Should be updating it next week. But it'll give you an idea of what you can do.
Just don't wrap it with html, that'll screw up your forums operation............