Yahoo groups has instituted another policy without informing its users. They are using web beacons (cookies) to track users OUTSIDE of Yahoo's sites. You can opt out of this program by going here: http://privacy.yahoo.com/privacy/us/pixels/details.html After you click on the "opt out" link, pay attention to the next page. The gray button that comes up CANCELS the opt out, so don't click it.
