are they "fine scratches" ?
What was there before the magic eraser was used? If they were dull white marks, it could be water damage like Steve says. If they are fine scratches, then you could buff them out using an automotive polishing compound and a soft cloth. There are "cures" for water marks on the web, but I'm not familiar with those.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)