Make your errors really stand out with this Conditional Formatting trick.

1. Select the entire sheet
2. On the main menu click Format then Conditional Formatting…
3. Change “Cell Value Is” to “Formula Is”
4. In the box to the right of “Fomula Is” type =ISERROR(A1)
5. Click the Format button…
6. Select the Format tab and pick a color, hit OK, hit OK