How to hide adsense iframe/div when no ads for this box are available?
Get the name/ID of the iframe and just use .hide()
If you can't find a suitable selector, wrap the ad in a div with an id e.g.
<div id='some_google_ad'>
// Google add code goes in here
</div>
and in your javacsript
$("#some_google_ad").hide();
Note there is no way of telling if your ad or ads are showing a community service announcement or a paid advertisement.
And I would suspect that having an adsense ad container on a page and having it hidden would be against the adsense TOS.
If its thoroughly empty then the folloing should do the trick : $("div:empty").hide();
This code is untested, as I do not know the structure of ad sense. But let me know how it goes.
This makes use of the empty selector that is available in jQuery.
Description: Select all elements that have no children (including text nodes).
much better idea: http://www.google.com/support/adsense/bin/answer.py?hl=en&answer=21590&rd=1