Thanx, undseth i've solved my prob.
and thank you NitroLiq, because with this site i'll be a ble to create more realistic glass..

Well, the prob was the bottom pice of glass (as you know i used nurbs cube), i just erased that and was ok, but if i want it to be like a cube i don't know what to do...maybe this site will help me.

Thank u.