Actually we always say that "за" and "перед" are used with Instrumental :), so if you know how to form the instrumental case, the formation has no problem.

Great article! Prepositions are always the hardest part of any european langauge!

I have a question though. I have never heard of an ablative case as it relates to Russian (in fact, I am only familiar with nominative, genetive, dative, acusitive, instrumental, and prepositional). Could you please expand on what dfferentiates it from the other cases, specifically the dative case, its use, and its formation?

Thanks so much!