Readers of the on-line magazine Salon -- the War Room is my favourite section -- may have noticed that the site's recent redesign doesn't visibly distinguish visited from unvisited hyperlinks in the main article listing on the home page.
Fortunately, the Stylish extension for the Firefox browser allows one to override a site's CSS styles. I use a few Stylish styles to re-colour del.icio.us in a soothing light green tone, simplify Slashdot's layout, and ditch the sidebar ads on BoingBoing.
Since my goal was so simple, it took only a minute to set up a Stylish style that correctly colours Salon's visited links in the same shade of purple used elsewhere on that site.
And if you like that, try my Greasemonkey script to force the Globe and Mail site to display the print-preview version of its articles.