Hi I'm fairly new with functions. I am working with Excel 2003

I wrote a simple function =SUM(A1,A2)
The cell the function is in is cell A3.

What's weird is, the formula is always displayed in the A3 cell. Not in the
background.
The spreadsheet was started by someone else. Would they have some kind of
format that causes this? I've never had this problem before.

Hope I explained this right.
Thanks for your time
Amy