I posted this question in WordPress Stack, but now they're telling me I should post in in Stack Exchange because this is probably a purely css problem.
I am developing a WordPress page with a fixed background, so the content area scrolls up and down. I guess it's parallax, or something like it. When I view the page in Chrome, the end of the content area meets the footer correctly, and the footer is the last thing you see at the bottom of the page. So far, so good.
But in Firefox, the content area scrolls upward another few hundred pixels, so that you can see the bottom of the fixed background picture below the bottom edge of the footer.
In order to understand the problem, view the following link in both Chrome and Firefox to see the differences. What I want it to do in Firefox is what it is doing in Chrome: