Firefox 4 not rendering a:visited::before (except color)

I'm making a custom stylesheet for a particular web site in Firefox 4. In it, I'm trying to prefix red 'x's to links that I've visited. Now, when I say making, I mean it used to work a while ago, and at some point, these 'x's stopped appearing (though the rest of the stylesheet works just fine).

Now, a:before (and a::before, per CSS3) works fine. a:visited works fine. Neither a:visited:before nor a:visited::before works at all (well, almost).

During my play-testing, I left in a::before, and still had my a:visited::before declaration to use red 'x's. For non-visited links, the a::before content was the same text color, but for vis开发者_开发技巧ited links, the ::before content was the 'right' color (red).

Here is a pastebin of the CSS at one point: http://pastebin.com/6Tzy1Q87

And here is a screencap of what that CSS resulted in: http://i.stack.imgur.com/rtw9L.png

Notice that the a::before simply specifies the content to a checkmark. The a:visited::before should change the weight, color, and content, but only changes the color.

I heard about a recent security 'feature' regarding Firefox and page history, but as I understood it, that would affect the regular a:visited selector as well.

Selectors including :visited are only allowed to change colors in Firefox 4, yes. That applies whether or not ::before is involved. See http://dbaron.org/mozilla/visited-privacy

I'd be curious to see what CSS you had that allowed you to change something other than colors using :visited.