Getting Values Of NaN In Floor Are Ratio (FAR) Calculations

I have a form which is used to calculate residential Floor Area Ratio (FAR). The form is structured into seven parts as follows:

Part A: Maximum FAR and Floor Area:

Part B: Gross Floor Area of the main floors of the main house:

Part C: Gross Floor Area of the basement or cellar:

Part D: Gross Floor Area of the attic:

Part E. Gross Floor Area of all accessory structures except detached garages: (including cabanas, guest houses, caretaker's cottages, pool houses, sheds, barns, or other structures except a detached garage)

Part F. Gross Floor Area of the garage: (not including basement garages)

Part G: Total Floor Area:

The Javascript involved in the calculations is as follows:

[CODE]

<SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript">
function checkAllInputFields(){
IsValidEntry(entireForm.A1.value)
IsValidEntry(entireForm.A5.value)

[Code]....

I have attached the html file as a .txt file for reference, and I have attached a .txt document including all the values I used for testing.