node editor and render turning out grey or black(see attahced images)

I have the follwing texture black white clouds added as a diplacement map. I have checked the node editor connected the materials to following nodes. When i render the animation of the frame or a single frame the render is dark grey or black.


Why are you connecting the render layer to the alpha channel of the Composite node. Connect yellow output to yellow input

For your render problem you have supplied insufficient info.
Rather than having to list al the possible causes please just supply a link to your blend file