This is a simplified, Debian only, version of what worked for me, mostly from http://mcelrath.org/Notes/MathML. See also http://kb.mozillazine.org/Gecko:_FAQs_:_Linux_XFT_and_MathML This is with Debian testing as September 12, 2006

1. apt-get install latex-xft-fonts
2. install the Mathematica 4.1 ttf fonts into  /.fonts (use the unzip utility to unpack).
3.   setenv MOZ_DISABLE_PANGO 1

4. visit about:config and set font.mathfont-familyit to one of
   • Math1, Math2, Math4
   • CMSY10, CMEX10

   This is to get rid of the complaining about the missing symbol font.