Visited tags are displayed with the link color, rather than the standard link appearance: tag-you-probably-havent-visited will be grey right now, but when you visit it, it'll turn gold here, or red on main site. If you clicked that too soon, try this-other-unique-one or delete the page for one of these made up tags from your history.
It doesn't show up this way in post previews, which are always just grey, regardless of visited-ness. That's how it used to be, so this changed during the redesign.
This affects the appearance when visiting a tag without a tag wiki:
Apparently this might just be a feature of the redesign though, since it occurs this way too on Meta Stack Exchange:
(usual tag appearance is grey)
