This seems to work for me when the top level app is "Category"...
At the top level go to: Options > Application > Change Appearance > CSS
and enter the following:
span.node-snippet div.adsense {
display:none;
}
Then in your sub-forum description, check the "Description is in HTML Format" box and try something like this:
<p>The is a Sub Forum to test Adsense code.</p>
<div class="adsense">Here is where the Adsense code goes</div>
NOTE: Having the description to display as a paragraph (within "p" tags) defaults to showing a 1em margin under the paragraph. That may not be desirable on the top level app unless all sub-forum descriptions are set to be HTML and also include "p" tags. Also, depending how the adsense code is written, it may be preferable to dispense with the "p" tags in the description.
Let me know about any issues. (Remind me of your forum URL so I can check your code, in case the issues are caused by your existing customisations. I can then make sure a forthcoming post on GregHelp will cover such possibilities.)
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.