Avoid Numeric Heading Errors In Your Formulas
Often you will use numeric headings in your worksheets. For example, you may have a table that uses years for the headings (i.e. 2004, 2003, etc...) Sometimes these headings may incorrectly get included in the calculations for some formulas, such as when you use AutoSum to total a column which has a numeric heading. Excel's AutoSum sees the heading cell as numeric, so it includes that cell in the formula. This can easily happen and likely will lead to costly and embarrassing problems.
There are a couple of ways to avoid this error. One is to precede the numeric value with an apostrophe (i.e. '2004). However, my preferred method is to format all of the heading cells, often the entire row, as Text.