Yahoo is now using something called "Web Beacons" to track Yahoo
Group users around the net and see what you're doing - similar to
cookies.

Take a look at their updated privacy statement:

http://privacy.yahoo.com/privacy/us/pixels/details.html

About half-way down the page, in the section "Outside the Yahoo!
Network", you'll see a little "click here" link that will let you
opt-out of their new method of snooping. I recommend doing this.
Once you have clicked that link, you are opted out. Notice
the "Success" message at the top of the next page. Be careful because
on that page there is a "Cancel Opt-out" button that, if clicked,
will *undo** the opt-out.