Are you trying to import the products and getting this validation message ? This is raised when the value for categ_id, ie, category is not specified while creating product.
So in your case, does it specifies line number along with the validation ? Will recommend using the batch import if the version is latest or to split the files into smaller sizes and import, so it will be easy for you to trace.
GOSH! I got the answer, some of the categ_id line were empty, that is why its error appear all the time!!