Not what the AdSense guidelines are.
Kaf, I've posted ads limitation, Not to teach/discuss AdSense guidelines, but for the sake of some first users:
who might have asked, why there are not ads in rest of other posts?
Slipping the ads between posts 1-2 and 2-3, but not between the remaining posts on the page, is what we are talking about here.
For, the ads:
1. He has placed Half text ads inside the loop, near footer in post.php.
2. Next he has Large Rectangle in index.php below page navigation
As per AdSense guidelines, only 3 text ads can appear on a single page, that's why he has got:
a. 2 Half text ads in first two posts.
b. 1 Large text ad in below page navigation.
Counting to 3 text ads, so no more Text ads can appear on the index page.
Had, he not entered "Large text ads" under page navigation, he would have got 3 Half text ads, in his first 3 posts, instead of two.