I wanted tables with no borders at all, after mucking around for a while with the CSS I found that:-
table.docutils, td, th { border: 0 }
works, but that:-
table.docutils td th { border: 0 }
doesn't work.
According to CSS documentation those commas are wrong but they've made it work for me. Is this just a quirk of Firefox (2.0.0.12 on Linux) or am I missing something (quite likely!)?