Rules for what a name can and cannot contain

The name cannot include spaces but underscore characters and periods may be used as word separators -- for example, Sales_Tax or First.Quarter.
It cannot look too much like a cell address... For example, you cannot name a range of quarterly sales "Q1" because Q1 is a cell address.
The first character of a name must be a letter or an underscore character. The first character of a name cannot be a number. Remaining characters in the name can be letters, numbers, periods, and underscore characters.
A name can contain up to 255 characters.
Names can contain uppercase and lowercase letters. Names are not case sensitive.