One of the many painful things about using Yahoo Search Marketing (when you are used to Adwords) is finding out how to exclude keywords or phrases from triggering your adverts. For example if you bid on ink but only sell red and blue ink you might wish to exclude green orange etc. Not a particularly good example but slightly better than widgets.
Unfortunately what is really simple in adwords (add a keyword/phrase with a minus (-) sign in front) takes 7 or 8 clicks on Yahoo SM. This video takes you though the clicks needed to find the right place.
PS. If you were bidding on Ink I would have a very long list of negative keywords or the traffic is going to be very poor quality