What does this mean: "error failed to link shader program."

Hey, hate to start posting with an error query but I cant find any reference to this issue on the forums or in the documentation:

the error message also says: " Pixel shader sampler count exceeds MAX_TEXTURE_IMAGE_UNITS (16)"

Error arose on adding a sphere to the scene with an ‘earth’ texture -
the scene - simply me playing with light in darkness - is here:


You have 12 dynamic lights in that scene. That’s a heck of a lot of lights. Each light increases the complexity of a shader. Consider removing some.

ok thanks - understood