You can add the nav bar with the following menu option: View->Show/Hide->Site Navigation Bar->Show Always.
It's just a matter of adding tags that look like this:
<link rel="HOME" title="Forum Index" href="https://ubbdev.com/threads/php/ubbthreads?Cat=" />
The above will make the "Top" button link to the forum index, with the text "Forum Index" showing as tool tip.
The only thing is that the link tags should be in the head of the document for it to be xhtml compliant (it still works with it in the body though), so it might be necessary to rearrange some code to get all link information before the send_header() function is used. It might be possible to move the send_header() to the end as well, and it just above the other places where it might be necessary, like before an error page is shown.
But if this only works in Mozilla I'm not sure if it's worth it, although it would be a nice feature.
