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. Once you have clicked that link, you are
opted
out.

Notice the "Success" message the top the next page. Be careful because
on that page there is a "Cancel Opt-out" button that, if
clicked, will "undo" the opt-out. (It looks like the "confirm opt-out"
button many e-mail spammers use.)

Those who use multiple browsers will need to do it once with each
browser.