Combine wine, water, salt, dill weed, mustard, lemon slices and butter in a large skillet.  Heat just until boiling.  Add salmon; cover and simmer 15 minutes, or until fish flakes with a fork. 

Remove fish and lemon slices to heated serving platter.  Stir corn starch into 2 tablespoons cold water in a small bowl.  Blend corn starch mixture into pan juices, stirring constantly until mixture thickens and becomes clear.  Spoon over fish.  Serve immediately.