But you can't identify which links are visited... because of security issues I described. Sorry my english is horrible maybe I described it very in a very bad way.
You can't with javascript, but the a:visited selector works in pure CSS, doesn't it? I'd like to do it so that I don't know which links you actually visited, but you would see them in a different color anyway. I think this should work somehow, I'll have to make some more tests.
https://bugzilla.mozilla.org/show_bug.cgi?id=147777
It is fixed in modern browsers now...