Suggest a better place for some of our users.

Leverage old css history hack for browsers that still "support" it
(Opera?), newer FireFox won't allow styling of :visited links, but
it still caches them and loads differently, so we can (try to)
detect this statistically. No solutions so far, but these papers:

https://w.n0l.ch/attachments/download/2/Browser_Timing_Attacks.pdf
https://w.n0l.ch/attachments/download/3/US-13-Stone-Pixel-Perfect-Timing-Attacks-with-HTML5-WP.pdf

look promising.