[TwoD]

You could add

Code:

document.getElementById('Content1').style.width="";
document.getElementById('Content2').style.width="";

right after

Code:

SET_DHTML("Content2", "Content1");

But that would just be a hack to get it working in FF, and it might break it for other browsers.

I suggest you try the Validator and fix all the issues it reports first, that might fix the cause of the problem and not just the symptoms (hopefully).