Tracking via your web browser fingerprint
I saw an article on web browser fingerprinting. As cookies become easier to block and thus less useful, browser fingerprinting maybe the next evolution in tracking users across the internet. It works by pulling configuration and setting information from the browser to uniquely identify you. Unlike cookies, browser tracking is hard to detect and harder to block.
If you want to know whether your browser has a unique fingerprint, check out the EFF's Panopticlick website.