Ajax popups on Firefox

I was working on fixing an Ajax popup that wasn't displaying on Firefox. Saw that the script was erroring-out on this line:

event.cancelBubble = true;

Found the solution near the bottom of this thread.

So now the popup appears, but it shows blank on Firefox (fine on IE). The problem had to do with setting .innerText. Need to use .innerHTML or .textContent for Firefox. Got that from this thread.