Pseudo-classes are selectors that use information that is outside of the document tree. The information that is not in the attributes of the element. This information can change between visits or even during the visit. Pseudo-classes always have a colon followed by the name of the pseudo-class.
There are two mutually exclusive link pseudo-classes, namely, :link and :visited.
This selects links that have not been visited. The syntax is as follows:
:link
This pseudo-class exists on any anchor element that has not been visited. The browser may decide to switch a link back after some time.
Here is an example along with the :visited pseudo-class. Here is its HTML:
<a href="#test">Probably not visited</a> <a href="https://www.google.com">Probably visited</a>
Here is the CSS. We can make an assumption that you have visited Google, so the link would likely be green in color:
a:link { color: #ff0000; }
a:visited { color: #00ff00...