An error value is the result of a formula that Excel can't resolve. The seven error values are described in Table 12-2.
Table 12-2. Error Values
You attempted to divide a number by zero. This error usually occurs when you create a formula with a divisor that refers to a blank cell.
You entered a name in a formula that isn't in the Define Name dialog box list. You might have mistyped the name or typed a deleted name. Excel also displays this error value if you do not enclose a text string in quotation marks.
You entered a mathematical formula that refers to a text entry.
You deleted a range of cells whose references are included in a formula.
No information is available for the calculation ...