Add keyboard command for "top menu" in preview mode.
Set Mozilla's idea of the pixel aspect ratio to match video pixels. (For extra credit, scale preview mode to correct for the differing aspect ratio.)
Add support for videos in preview mode.
Disable scrollbars (not sure how how to do this).
May need to override default menu navigation actions because dvdauthor seems to cause rather undesirable behaviour when buttons are not arranged in a grid.
Search whole of history rather than just previous page when deciding whether a link goes back or forward.
For any page with no links, add a "back" link (this raises the issue of localisation, of course).
If a page is too large, split it and add "next" and "previous" links (seems very difficult).
