To hide gridlines in a selected area of a worksheet, follow these steps:
Select the range of cells for which you want to hide the gridlines.
On the Format menu, click Cells.
Click the Patterns tab, and then click the color that matches the background color of your worksheet (typically, white).
This hides the gridlines on all four sides of each cell in the selected area.
To restore the gridlines around the perimeter of the selected area, click the Border tab. In the Color list, click the color that matches the color of the gridlines on your worksheet (typically, gray-25%), and then click Outline.
The gridlines are hidden in the selected area of the worksheet.