Can you over-knead bread?
Yes, you can - this will result in a dense, solid bread. If you're kneading by hand, it's unlikely that you will over-knead. If you are using a mixer, the dough will be ready when it pulls away from the bottom and sides of the mixing bowl. Another way to check is to pull a piece off a pull it in different directions - if it snaps, it requires more kneading.