WordPress MU

how do i put an adsense banner under the first post only on every wpmu blog?

The same way you do with regular wordpress:

http://www.tamba2.org.uk/wordpress/adsense/

Great ty, adsense worked fine, but with some other ad-distributor I have a problem, theres is ' ' in the ad-code so I just get errors?

Ask the plugin author.

no php interpret the ' in the ad-code as the end of the text php is supposed to echo.. thats the problem..

Well, it's an adsense plugin, so you need to be talking to the plugin author for support.

Example : http://www.hitnews.net main page

code :
-------------------------------------------
<?php $postcount++; if($postcount==1){?> <div>

Adsense Code

</div> <?php } ?>

Which is discussed at the link given above.

no drmike, that link you gave works great for adsense, but not for ad-code which includes both " ' ; in the ad-code itself.

the solution, (worked for me)
replace every " with \"

$ad-code = " strange-ad-code ";

then echo $ad-code;
instead of echo 'ad-code';

The code works fine, but my first ads are always irrelevant. Only after when I click on the post will the ads change to something more relevant. I think it has something to do with my meta tags. Any ideas?

<!-- google_ad_section_start -->

<!-- google_ad_section_end -->

https://www.google.com/adsense/support/bin/answer.py?answer=23168