When switching from K-Meleon to Mozilla as my main browser (MWAHAHA), I discovered it steals the focus from the text fields to the radio buttons on Kit's news page. (Mozilla 1.1a+, the 9 July 2002 build.) I thought I was doing my JavaScript for selecting the radio button wrong, but after messing with it a bit, my new theory is the click event is bubbling beyond the text fields to the label tags they're inside, and so triggering the "Focus on this label's target" imperative.
I may just break up the labels rather than submit a bug or anything, since it's not clear which behavior is "right." According to where label is described in the HTML spec, it's legal to have inputs; since it takes care to say it's OK to put multiple inputs in a label as long as the input for which the label exists is explicitly given with the for attribute, it seems to imply my behavior is desirable (since the current behavior is unuseful), but I dunno.