App Exposé Window Ordering?

When App Exposé shows my browser windows (i.e., 4-finger swipe down or Control-↓), the order of the windows changes from one time to the next, and I cannot find the window I'm looking for easily. (What I'm really after is an efficient way to flip back and forth between the two or three most recently used windows in an application, but that's another story.) Can anyone tell me if there is any logic to the ordering of the application windows in App Exposé, or if it is just random?