Tip: If you place a moon, midpoint, or dragon coin through Map16, it will always respawn whenever you reenter that sublevel. It will not respawn if you add it through the Add Objects/Extended Objects window.
I think there used to be a list of recommended browsers (if it still exists I can find it), but anything that counts as a "modern" browser would probably work best. (i.e. the newest versions of Firefox, Edge and Chrome.) IE probably won't.