Javascript Calculator no longer works in FF. Other browsers OK.

Question

I have a javascript calculator that has suddenly stopped working in FF. I have upgraded from 3.5.8 to 3.6.3 but no changes. IE, Safari, Chrome and Opera all work fine.
Calculator can be found at http://www.hydrastop.be/hprodCalc.html

Answer 1

I see that the answer that I posted yesterday got lost by restoring a forum backup, so I'll repost my answer.
I see that you have already applied the change that I had suggested.
You need to use document.getElementById.
See https://developer.mozilla.org/en/DOM/document.getElementById
<code>function doMath() {
var one = eval(document.theForm.elements[0].value);
var two = eval(document.theForm.elements[1].value);
var m2 = Math.round(one * two);
var m3 = Math.round(one * two);
var maxhstopqty = Math.round(m2 / 5);
var minhstopqty = Math.round(m2 / 8);
var minhblockqty = Math.round(m2 / 5);
var maxhblockqty = Math.round(m2 / 3);
document.getElementById('squareMeters').innerHTML = m2;
document.getElementById('squareMeters2').innerHTML = m3;
document.getElementById('minhstopReq').innerHTML = minhstopqty;
document.getElementById('maxhstopReq').innerHTML = maxhstopqty;
document.getElementById('minhblockReq').innerHTML = minhblockqty;
document.getElementById('maxhblockReq').innerHTML = maxhblockqty;
</code>