inc_catsmenu and FireFox

Could you be a bit more specific about what doesn't work?  Does the generator fail?  Do your pages not render correctly?  Could  you post a link?

That is not the default menu.  Your UpDown function does not select an object.

It should look like this:

var etab=document.getElementById('SUB' + tabid);

The point Matt is making is that you are using code for the menu that is not the stock code from ProductCart.

The process of altering the code (in inc_catsmenua.asp) to remove the +- icons evidently resulted in a situation where the javascript is incompatible with FF.  There are also display issues with FF, such that the pages shift to the left whereas they are centered in IE.

That menu is not part of the ProductCart v3.x

Try this:

1.) Open inc_catsmenua.asp

2.) Find
var etab=eval(tabid);

3.) Replace with:
var etab=document.getElementById(tabid);

4.) Save and Upload.  Be sure to backup your existing copy first.