Asking for your salary level is a fair question and a standard part of information gathering. Conversely, asking what the range is that's being offered is also fair, but sometimes withheld because it may spoil future negotiations. You could respond by saying something like:
► "I'm flexible and especially interested in your company and this position. What is the range being offered?"
You will usually get a factual response that the position will pay in the $X to $Y range depending on qualifications. But be prepared for a response such as:
► "The range is open and we usually offer what's necessary to hire the right person. But first I need to know if we are on the right page. What are your expectations?"
Again, avoid boxing yourself in but if pressed give a wide range and state that you are flexible and feel as though you could come to mutual understanding when the time comes.