This problem means that the long muscle that runs down the front of the abdomen does not meet its partner in the middle. So this can increase the appearance of an overweight stomach. However if you can maintain your ideal weight through a combination of diet and exercise then it should be less noticable.
Exercises to work on the other abdominal muscles may be work trying to help tighten the stomach...but do make sure that you see a physical trainer first to get a personal plan for you. Useful exercises may include working on oblique muscles with waist rotational twisting.
Divarification of the recti is considered a cosmetic problem and surgery can be used to correct it, however the surgery may not give you a permanent result so it not always recommended.