By default, gridline is not printed on paper. Nevertheless, I would usually remove gridline when I submit my report, or paste part of a spreadsheet into PowerPoint or Word. Why? Simply for better look and feel.
See the screenshots below to see the impact:
By simply taking out the gridline, the same presentation looks better instantly.
So why you keep your gridline in your report? Probably two main reasons…
- Lazy
- Don’t know how to remove gridline
For the former one, I could offer you no help. ;p
For the latter one, here’s the simple step to remove gridline: Uncheck the Gridlines
Excel 2007 or later (Ribbon –> View Tab) 
Excel 2003 (Tools –> Options)
Btw, I have seen many people using a trick of applying WHITE FILL to cells of whole sheet in order to get the same visual effect. However, I would not suggest so. Have you ever seen a color printout on colored-paper? Can you imagine what it looks like if all the cells are WHITE filled?
wmfexcel 