Visited link … by CSS

I read this article this weekend and I was really fooled by the simplicity and the efficiency of the proposed script. The author explains how he can find visited sites by using only the CSS property visited of a hypertext link.
How does it work?
In fact in the page the author « hidde » a list link of the sites he wants to test.

He also has defines a particular css property for the visited links

a:visited {

Then your browser makes the rest by marking the links you have already visited. It remains to go through these links and to test their offsetHeight property.

var items = document.getElementsByTagName('a');
for (var i=0,i

Simple and effective ....