Tracking your Browser Without Cookies
How unique is your browser? Can you be tracked simply by its characteristics? The EFF is trying to find out. Their site Panopticlick will measure the characteristics of your browser setup and tell you how unique it is.
I just ran the test on myself, and my browser is unique amongst the 120,000 browsers tested so far. It’s my browser plugin details; no one else has the exact configuration I do. My list of system fonts is almost unique; only one other person has the exact configuration I do. (This seems odd to me, I have a week old Sony laptop running Windows 7, and I haven’t done anything with the fonts.)
EDITED TO ADD (1/29): There’s a lot in the comments leading me to question the accuracy of this test. I’ll post more when I know more.
EDITED TO ADD (2/12): Comments from one of the project developers.