Web Beacon
New word to me: web beacon. It means an image on a web page that has a unique name so that a request for it can examine already stored cookies and send new cookies—all for the sake of tracking people’s paths around the web.
I first read about this in Wired a year or two ago, and they described how companies send out HTML spam with these web beacons (although this term wasn’t used then) in them, in order to know when a spam message has reached its final destination and been opened by someone. This is valuable information, I guess.
This page at Yahoo describes their policy regarding web beacons. They have a link so you can opt out, but it seems to set a cookie so you’ll have to opt out from every browser on every computer you use.