This is definitely not cool. I know Firefox for version 4 is slated to have a way to hide the history, but its not been said how they will address it.
From what I’ve heard, browsers are designed for allowing access to this history. There’s even a website that can show you a number of places you’ve visited just by displaying their page. It is either through the history or through deciphering the cookies.
As I’ve said many times, “It will be amusing with the hacker scum discover that Firefox and other ‘Not Microsoft’ browsers are as fun to hack since they are as or more open than IE now.” This is a case where by trying to kill IE, they might be making it into the most secure as it has to defend the most.
My understanding is this: a page will display visited links in different colors. The javascript can then query the color of any given text element. Hence, you can create a hidden page (iframe) that can check to see if you've visited specific web addresses.
This is something that should be of great concern to all FReepers - it is very easy for, say, a government website to check if you've been to http://www.freerepublic.com! (If that link is discolored - which it certainly should be for this crew - then javascript can detect you've been visiting it....)
Can you post the name of that site?