here is a paragraph from the microsoft 2004 annual report

[Jonathan Hutchins]

On Wednesday 27 October 2004 09:30 am, D. Joe Anderson wrote:
> On Tue, Oct 26, 2004 at 04:47:40PM -0500, Jonathan Hutchins wrote:

> > [Microsoft] did do a ground-up rewrite of the mosaic code for their second
> > release of Internet Explorer - something that would be a vast improvement
> > if Mosaic were to do the same, especially with modern considerations and
> > security.  There are still bugs in Mozilla that I recognise from very
> > early releases  of Mosaic.

> Isn't that what Firefox is about?

I don't think so.  From what I understand it's just regular Mozilla that's 
been stripped of some "features" and cleaned up a lot.  Not a ground-up 
rewrite.

This is PC code that dates back to 1992.  Mozilla has never gone through and 
integrated all the accumulated cruft, or re-written the code that says "if 
2+2=5 the answer=4".  The patches that fix patches that fix problems that are 
still in the code are still in the code.