There are three different things that have happened.
1: the site is loaded all fine
2: the site is loaded all fine, then the content part (included with php) disappears (after having been shown for a short time)
3: the content part doesn't appear at all
The odd thing is that if you view the code, the content part is there. (Starts after <div id="tekst">, line 45)
I have tested with several browsers and it has happened with all of them. the (not so good) solution to the problem is refreshing the site untill all the contents have appeared