Well, Hovereel, I take it you're new to Uncyclopedia, so welcome! In this article, you make some mistakes that every Newbie does. First off, because of the nature of the article, your laughs are restricted to a certain group of people (Europeans), which isn't very good on such a diverse wiki. Second, you have way to many statistics and lists, which i'll get to in the P&F section. Also, you sort of drift off into randomness in the Cultural Signifigance section- randomly inserting famous people into the mix never makes an article funny. I suggest reading HTBFANJS, and then adjust the article accordingly.
As stated above, very few people will get this article. For those of us who have never heard of the Danube, we sort of just get turned off by this kind of article (a more impulsive user might put it on VFD). I recommend presenting your article so that it is both informative and entertaining at the same time. A good idea would be to copy and paste the first sentence from the Wikipedia article, and from then on out, switch between informing the reader and making him/her laugh- that way, your article will be more presentable, and more open to edits and expansion.
Prose and formatting:
You should probably proofread this, as I spotted several spelling errors. You make a major (albeit common) mistake throughout the article- lists. Lists, as a general rule, are almost always boring, unfunny, and tedious. Take the lists in the "Tributaries" and "Important National Parks" and make them into paragraphs with the ideas from the list. Articles always look nicer when they are in paragraph form as opposed to lists.
There aren't any. Image wise, there are a few things you should probably do: first, a picture of the Danube itself, in order to clear any doubt as to what your article is actually about. Second, perhaps a map of Europe in the "Origin of the name" section, in order to specify where it is. You're going to have to get creative with the rest; a river article has some interesting possibilites image-wise.
My overall grade of the article.
Well, you're new here, and since this is your first shot an article, it's understandably of poor quality. However, there are quite a few things you can do to fix it up! First, get rid of your lists throughout the article- taking those out of the picture will make your article look better. Second, expand your concept so that it appeals to more people- like I said, take some facts from Wikipedia and put some humor in them. Third, get rid of all statistics and numbers- those are different then facts, they're just bothersome. Finally, remove all the random celebrities and in-jokes from your article- I would recommend just getting rid of the "Cultural signifigance" section altogether. Also, take a look at HTBFANJS-it's a helpful guide.
Bottom Line: Bad article, but easily can be fixed up if you follow the advice. Good luck! =)