Why do some sites use line-through for the a:visited style? A person who visits a page may want to go back to it. It’s not unusual. It is important to make it obvious when a visitor has visited a link because she may be looking for something and wants to check the links she has or has not visited.
Using the line-through value makes it hard to read the link. In case you haven’t seen line-through, it’s much like strikeout; it puts a line in the middle of the text as opposed to beneath it like a regular underline.
For a while, it was in style to make the links the same color no matter what — even if it’s visited, hover, active or plain ol’ a:link. I did it on my site and quickly learned it impacts usability — in a bad way. So that feature didn’t last long and it’s not cool.
While you’re surfing — pay attention to the links. You may not realize the importance of their colors until you think about it. It’s a subconscious thing.
Yesterday, I came across a site where its link color was lime green on a white background. That hurt to read. Contrast is also important when it comes to links.
At one point, I used dark orange visited links on a regular orange background. Bad move as no one could read it without straining. So think about those links while you’re traveling the Web and see how much of a difference they make.
Current version of my site (which is slightly broken) uses bold dark blue with no underline for all links, but my long-overdue redesign will be more polite. Nowadays I encourage leaving links unstyled: people are used to blue underlined for unvisited links and purple underlined for visited links; it’s just confusing to change it. It’s like restyling buttons to look like abstract icons; very un-Nielsen.