Privacy flaw in IE and Firefox

If you're worried about websites knowing where else you've gone, then you need to make yourself aware of this. The technique is to put a bunch of links on your web page and then use a script to see if they trigger the specific style you've inserted for :visited. If coupled with some Ajax type stuff, it could be set up to keep sending and testing links for as long as the visitor has the page loaded. Even though this whole weakness has been known for some time, apparently only Opera has any built in defenses. See some more discussion about this issue on reddit.