If you look at [this page](http://www.xn--existenzgrnder-im-netz-1lc.de/), you see 3 boxes (div#threeBlockOnTop), and a long box below (div#squeeze) with random content. The blue gaps over and under the 3 boxes should have the same size (around 30px). But in Firefox the gap over the 3 boxes is wider, because for some weird reason it is influenced by the top margin of the element below. 

If you play with margin-top of div#squeeze in Firebug, you can see how it also changes the position of the 3 boxes above. What is wrong? And does that involve some legitimate property of CSS, that could be used for good?