Hello! I have a problem! I just try to add an enchanted weapon in Oblivion. I save my work and when I try to exit from Construction Set, I get some strange (for me) warnings.
They look like this : "ModelLoader still has 4 NIF files", "1-furnituremarker11.nif", "1-furnituremarker02.nif" etc. And the weapon don't appear in the game.
Can anybody help me, please!

The error message are somewhat standard and you do not need to worry about them.
As to your weapon not showing up in the game, most likely you ned to do a clean save first.
Load your game without your mod active. Save it. Load your game again, this time with your mod active.
You'll probably find your weapon now.