Why scrollWidth doesn't work in this case in Firefox?

Question

I\'m trying to make a simple marquee in Javascript, and need to get the full content width of innerDIV in the following:

Answer 1

This seems to do the trick:

docWidth = Math.max(
        Math.max(frameDoc.body.scrollWidth, frameDoc.documentElement.scrollWidth),
        Math.max(frameDoc.body.offsetWidth, frameDoc.documentElement.offsetWidth)                               
);