This used to be possible, but browsers put into place various mitigations: restricting which properties a :visited selector can affect, always computing both th

This used to be possible, but browsers put into place various mitigations: restricting which properties a :visited selector can affect, always computing both the visited and non-visited style to avoid timing attacks, etc. http://dbaron.org/mozilla/visited-privacy http://dbaron.org/mozilla/visited-privacy has a writeup describing the issues and the solutions that were adopted.