Not "every website" in browsing history
"a website that demonstrates just how easy it is for a webmaster to detect every website contained in your browser history."
It cannot detect every website or URL in your browsing history. It loads a long list of domain names, such as http://startpanic.com/db/db_en.txt, and then creates a hidden iframe that contains various links built from those domain names. Then it checks the computed style attributes on those links to see which have been visited.
So, it may detect that you have been to youtube, but it has no way to tell which videos you saw or how many.