This is something that annoys me intensely and the biggest culprit is Apple, which insists on delivering all content to me in German, though this is a language that isn't even spoken where I live (the French speaking area of Switzerland). I suppose this is part of Apple's philosophy of always knowing what's best for you.
I've discovered that most sites include some kind of option to change the language, though sometimes you do have to hunt for it. Also for some reason, it will sometimes revert back to something else even though you've done nothing.