I have been advised that, when entering information into a CSV file that I'm going to use for an upload, I should make sure not to click on any empty cells in the file if I'm not going to end up putting data into those cells. The person who told me this said that if you click into one of those cells, there is some kind of background data that gets put into that cell in the CSV, and if you do click into one of these empty cells, you should delete the cell so that the CSV does not error out when you are trying to upload it.