@Moon oddly enough, I think there's a provision that disabling all cookies must be as easy as enabling them all. Not that any of those implementations really ever gave a fuck.
@Moon@cereal Forget Me Not extension for Firefox is also quite good. It clears cookies when you close the tab/leave that domain. They will still ask you whether you want cookies or not every freaking time! So the most complete solution would be to avoid such web sites 😆