Document.box.b9 is null or not an object Why am I getting this error?

Hi,

I am trying to upgrade one of the calculators on my website. I have eliminated a lot of the lines from the program and uploaded it here: http://www.1728.com/keplerTEST.htm
All you have to do is press "CALCULATE" and you'll get the Document.box.b9 is null or not an object error.

The thing I find so frustrating is that I have used this exact method for rounding a number (with the user selecting the number of significant digits) on dozens of calculators on my website with no errors.
It is not the rounding routine that is causing the error. It has to do with the entry box at the bottom and it creates an error without even changing the number.
For example, here is a recent calculator I wrote that works just fine:
www.1728.com/gradient.htm

How come it is not working here?

All you have to do is press "CALCULATE" and you'll get the Document.box.b9 is null or not an object error.
Javascript expects to work with viable markup, and you have two unclosed forms.

Hi Arty,
You just earned "thank you" number 50. :thumbsup: Successful !!!

In case you want to see the modified program, it is located here:
www.1728.com/kepler3.htm

I can't believe I forgot to close the form. (Actually, there was only 1 unclosed form but when I edited the "TEST" version for everyone to view, I deleted another closing form tag.) :o
Thanks again.