Even if the problems were made by Mensa members (from what I understand it’s someone from Czech Mensa, so the problems might be slightly different here in the UK! Besides, it’s only one guy’s “take” on the Mensa test), the test isn’t really a good indication of your IQ anyway. Mensa are quite secretive about the types of questions they use, although from what I remember one is the Cattel B test (non-verbal reasoning like the link you gave) and the other is verbal reasoning (e.g. “arm is to hand as leg is to…” – the correct answer is “foot”).

If you want a “proper” indication of your IQ, I’d take a Mensa IQ test at one of their test centres (check their website for details), but I think they can also post you a “home practice test”.

Hope this helps.