When you have metallic window screens, the sun tends to cook some kind of screen-like pattern of pollution on the window that doesn't want to come off. The key is to use any oven cleaner, which when you think about it, is made for cleaning off cooked-on matter. Be careful, the oven cleaner will strip the paint off of the window frame.
One of our viewers who is a grandmother sent in her long proven tip as to how to not have to polish silver very often. Just as soon as it is clean, dip it in any household cleaner, she uses Mr. Clean, shake it off but do not wipe it. Let it dry and the invisible soap film will keep the silver from tarnishing for a long time.