Making Your Outstanding Errors Stand Out
Although conditional formatting is most useful for alerting you to anomalies that crop up in your spreadsheet data, you can also use it to warn you when certain types of errors crop up that aren't related to errors in the formulas themselves. For example, you can use conditional formatting to flag errors in a typical sales table - one that totals the columns and rows of figures to ensure that the sum of the column subtotals and the sum of the row subtotals are always equal to the grand total at the intersection of the two.
Note that the only way the subtotals wouldn't equal the grand total is when you or a coworker accidentally deletes or replaces one of the SUM formulas that calculate a column's or row's subtotal. If you don't protect your formulas against this type of unintentional editing, you can at least set up this type of conditional formatting to notify you if such an error occurs.