Good news is that the issue is recognized by the Mozilla team at the very least:
>Pages with position:fixed banners/headers are all the rage these days. But when I try to read content inside one of these pages and hit Page Down or Spacebar, firefox calculates the page length relative to the whole browser window, not just the part visible underneath the position:fixed header. So it scrolls too much, and the first few lines of the next page end up hidden
That's great news. Do you know what release this will land in?
Edit: Oops, I guess it's already there. I couldn't think of a site with an appropriately sized fixed header to test it, but Google+ is such a site and pagedown works perfectly there. Nice.
Works for me on FF17. Does not work on Safari or Chrome.
BusinessWeek.com articles don't totally work. They seem to have an extra pop with their header. So 2 levels of BS. Can't totally fault the browser there.
Techcrunch.com works perfectly fine too.
So yes, fixed in FF17 and also seen to work on FF18.
>Pages with position:fixed banners/headers are all the rage these days. But when I try to read content inside one of these pages and hit Page Down or Spacebar, firefox calculates the page length relative to the whole browser window, not just the part visible underneath the position:fixed header. So it scrolls too much, and the first few lines of the next page end up hidden
>Status: RESOLVED FIXED
https://bugzilla.mozilla.org/show_bug.cgi?id=780345