Improvement yes! My German gives me some hints to what you have written, but anyways...
The first impression is that there is a huge white blob, oh wait thats an ad my Adblocker cleared out. Either way, there is a lot of white there on the side of the ad, and the ads seem more prominent than the content of the site. Ergo, that gives the impression of a landing page. Also the linkpartners on the right give that impression.
Its not that you have ads, but that your ads are featured and displayed in a way that makes them seem more important than the content. This causes problems for visitors because by now they have seen enough ads to know what they are. If they believe the whole page is ads (which is a possible assessment since many people give a site about a 2 seconds glance when searching before staying or leaving) they might not stick.
The lack of branding makes it seem like a landing page too. When you type a wrong address, it always puts that address somewhere in the top left as text. Here, could you manage a nicer design, or work with that?
I'm assuming your main hope is that this site will provide ad revenue. I urge you to seriously think about that assumption, because the overload of ads really just overwhelms the user. Here are a couple articles I found quickly. Its not that you can't have them, but rather that they should work with your content, instead of conflict with it. That is probably the main problem with both of the sites.
In closing, the colors are nice and the layout is clean and simple. When I have adblocker on (which cuts out the ads) the site is better. So I would take out the ads, and then find some simple but clever places to put them so they don't distract too much. You want people to think the ads are content so they click, so its a little bit of trickery, and a little bit of cunning to get the links right.
I viewed this site with ads and I agree that they are a bit too distracting, especially the one in the content section. At first glance it may be difficult to notice the six links underneath it.
I'd also recommend not having your "link partners" higher than any content. Maybe try putting them in the footer.
I like the menu at the top but it can obviously be improved. Maybe not have such a large spacing in between items, or have the background of an item change colour when you hover over it? Or you could put the menu inside something else (take a look at the top of this page to see what I mean).
With regards to your content on other pages (I was looking at moods) don't forget about a hover effect for your links underneath the images. Also, align your next, previous, first and last with the text "Moods : pagina # van #" so that it looks that little bit nicer. You could even have a hover effect on those images (just something simple like a colour change).
Overall, it is a clean looking website and I think once you remove/change the ads it'll definately look better.
Thank you both for your comments, I'll probally remove some adds and lower the linkpartner section, make the menu more attractive, and will add some hover effects. It probally will be changed in 2009, cause I'm quite busy at my work :S