I think having ~/.mozilla/firefox/$foo.default/chrome/userContent.css containing
@-moz-document url-prefix(http://news.ycombinator.com/) {
td { color: #000000 !important; }
a { color: #000055 !important; }
}
helps an awful lot with news.yc's appearance. The main improvement being the banishing of that awful low-contrast gray on gray text.