When visiting websites from Belgium, one frequently occurring annoyance is that websites will serve you content in French. This happens even when you're in the Dutch speaking region (this should be easy to detect since the ISPs are different between regions).

It's frustrating because many Dutch speakers can understand English better than French.

It would even happen for websites that support English, French, and Dutch, such as Skype.com (can't test if it's still happening though).