Electronic Frontier Foundation staff technologist Peter Eckersley has published some new research showing that individual browsers can be identified to a high degree of accuracy without cookies or other tracking technology. EFF has produced a tool called "Panopticlick" that tests how unique your browser is, and they're using the results from it to further their research:
Is your browser configuration rare or unique? If so, web sites may be able to track you, even if you limit or disable cookies.
Panopticlick tests your browser to see how unique it is based on the information it will share with sites it visits. Click below and you will be given a uniqueness score, letting you see how easily identifiable you might be as you surf the web.
Only anonymous data will be collected by this site.