What are some european countries to avoid on a europe trip?

I don't think there are any European countries that are especially dangerous... And since the war on the Balkan is over it shouldn't be dangerous to visit Serbia or Bosnia or Montenegro (okay, I'd skip Kosovo if I were you). A friend of mine traveled to Serbia last summer, alone (he was eighteen at the time), stopped at several places, including the Exit music festival in Novi Sad. Who knows, maybe you should check it out! I could also recommend Belgrade (Beograd) in Serbia and Mostar in Bosnia and Herzegovina. Also, if you're around the Balkan area, don't miss the Croatian seaside and on your way back to western Europe Slovenia and Hungary. They aren't too well known but they're all definitely worth seeing. So if you get fed up with France and Italy and whatnot, go southeast :P