That's right -- two great tastes that taste great together; the Mozilla browser complete with Gecko rendering engine teamed up with anti-aliased text through Fontconfig and Xft. Xft has been extended to support AA text both through the Render extension and the core protocol to make sure everyone gets great looking text.
These patches require current Fontconfig and Xft bits as distributed in fcpackage version 2.0 here. Get your Fontconfig and Xft and bits up to date, then download either the glibc 2.2-based build (done on Debian Testing) or a patch that you can apply to current Mozilla CVS. Building Mozilla from scratch isn't hard anymore; follow the directions on the web site and you can have your own custom version built in a few minutes (well, ok, a few hours).