This is a well known usability principle; it helps people navigate sites by showing them which pages they have seen already.
empirical observations from user testing have identified several severe usability problems on sites that violate this convention. When sites use the same color for visited and unvisited links, users:
unintentionally revisit the same pages repeatedly;
get lost more easily because their understanding of each link's meaning is reduced;
often misinterpret or overlook the difference between two similar links if they’re unsure about which one they've already visited; and
give up faster because they have a reduced sense of mastery when the site fails to reflect their actions and thus help them navigate.
We leave this up to developers. In applications, visited isn't useful and can actually be detrimental.
Sorry - do you have any evidence to back up that assertion?
I don't think buttons should have visitited illegible black color. nonsense
I think we should add this feature as if we has not add a:visited css style, the links that have clicked and the non clicked have no diffence.
In my project, i add it to page a:visited xxx,it solve the problem.
but as a base css lib, we should add this feature. If users found this is not what they want, just add another css style to override it. it become perfect.
Ironically, Jakob Nielsen forgot that Linkrot reduces the usability of the Web and moved the article about link colors without a proper redirect.
I don't buy the application argument, to me it seems like a decision in favor of visual appeal rather than usability. Thankfully, it's easy to override the way it is now, you just have to remember it for every website.
If you're using the less version of Bootstrap, you can try this Gist I made as a base: