Why doesn't ANYONE ever notice Jeff staring out at them?
It's only at the end of the movie that the murderer looks and sees Stewart's character at the window. I don't know about other people but whenever I leave my curtains open, I notice if people are looking in at me.
Also, don't they have any kind of insects in that neighborhood, especially in the summertime? Nobody has any screens on their windows. You'd have flies in the kitchen during the day and mosquitoes at night if you had no screens.