Microsoft Excel 2007 AVE (Average) function not working

Microsoft Excel 2007 AVE (Average) function not working.
I am new in Windows 2007. I previously worked on Lotus 123 and Quattro.
I know that Microsoft Excel and Lotus 123 and Quattro are the same in function.
Why can I not get the exact result when I am getting the average function in Excel 2007?
I got the result #NAME?
What does it mean?
This is the formula: D11 = AVE(D1:D10)
