Yes. You do not want to train your abs everyday. When you exercise your abs, you are causing small tears in the ab muscles. As you rest and recover, your allow the muscles to heal, and build larger. If you work them everyday, you are not allowing time for those muscles to recover, and rebuild.
Also, remember to see your abs, you body fat needs to be around 10%. To see real defined abs, the body fat needs to be about 6-8%.