I ran across this link earlier today, was a very interesting read and i thought i'd share: http://www.gnucitizen.org/projects/javascript-visited-link-scanner/ looking at the javascript source, it seems like it functions by generating a hidden link and adding it to the page, then determining whether the link is shaded as 'visited' or not by view the browser's internal coloring of the link. really quite clever. edit: site is back up