i made this render and there is a problem. i don’t know how to discribe it but you will see for yourself
how do i solve this?
Two duplicate objects in the same space, delete one?
Wow, I wouldn’t know how to describe that problem either. I would agree with Marklew, that’s my first guess. Another similar possibility is that you have duplicate faces that are made from the save vertexes. The simplest solution would be to “Remove Doubles” in edit mode and see if it removes anything.
Another option, which is somewhat less likely, is that you’re using a procedural texture (like clouds) and the “Depth” is too high. The depth for clouds can go up to 20. If you go higher than that, really strange patterny things start happening, kind of like what’s on that last bottle.
Hope that helps.
nope all materials are the same exept the text.
i used a cloud texture but the depth is only 1
and no doubles are removed.
Try recalculating your normals. Flipped normals tend to produce black artifacts in the render. 
if all else fails, do what i do: delete it and duplicate one of the others and change the texture (essentailly start again :P)
its fool proof
oh, and on the topic of improvement, some Ambient occlusion would look good here
AO here wound’t do much, in direct light you shouldn’t see much of it. A fill light to lighten the shadows would do much more, they should be abous as dark as the shadow on the bridge.