うっ。さっき知った。。。
Vimperator is a free browser add-on for Firefox, which makes it look and behave like the Vim text editor. It has similar key bindings, and you could call it a modal web browser, as key bindings differ according to which mode you are in.
2007/08/16付けでリリースされていた模様。気付くの遅すぎorz