too near ???

I learn openGL with nehe tutorials, and i have modified the numbre 4.
I have add a plane, behind the triangle.
The triangle has a 0.0 Z-depht, and the plane a -0.01 Z-depht.
When I rotate the scene, the triangle has a bad looking. Sometimes all is allright, and sometimes, he has strips ?
When I put my plane at -1, there are no problems !
Is that a z-buffer problem ?
Can anybody help me ?
Thanks, and sorry for my poor english

This is called zfighting. The zbuffer has limited precision and you need more separation between the surfaces. Moving the near plane away from the eye and bringing the far clip plane towards the eye will also help.