It really depends on how deep they are. If they're light, superficial scratches then a light abrasive (like toothpaste) could work for polishing the glass. Just apply a small amount to the glass, and scrub away in strong, fluid circular movements.
Just be careful and if you can, test this on another glass surface you don't mind ruining. You're dealing with abrasives here, and if you're not fluid enough or the paste is too abrasive, you might end up with even more scratches.