Original creator here. I'm super surprised to see this posted here.
I can answer any questions people have.
I can answer any questions people have.
The hundreds of grey boxes that you see are actually links to sites belonging to different categories like programming, science etc. and the red ones are those that you have visited (based on your browser history). The basic idea here is of using the CSS selector a:visited to highlight visited links in red, and by clicking the red boxes the users themselves reveal the sites they have visited. The website then uses this information to draw a pretty pie chart showing which categories the user is interested in.
The browser developers responded by minimizing what a ":visited" can do, so Javascript shouldn't be able to get direct, or indirect through CSS, access to that information.
Kinda weird.