"You are behind the tables."
Translation:Önök az asztalok mögött vannak.
You're right. I didn't notice it until now. Actually I confuse the postpositions sometimes. But I am concerned about something else here. The phrase uses "Önök", which is a 2nd plural pronoun, together with "vannak", which is a 3rd plural form. Why does this happen? Shouldn't it be "Önök...vagytok"?
This sort of "formal you" even exists in English, although it is rare and sounds old-fashioned or extremely subservient. One can use "sir" or phrases like "M'lord" and "M'lady" to address someone, and those all take third person verb forms. That's how I think of these constructions in Hungarian (and Spanish) to reconcile them with my native English instincts.
Right over your comment is mine - "Formal speech structures that you are likely to come across all involve third person conjugations." Nothing wrong with "vagytok" as long as there is no "önök", that's for informal.
And as always - please, read the comments before writing a new one.