[ Other - Internet ] Open Question : How to stop Firefox from remembering my Yahoo ID?

On the Yahoo Login page I click once on the Yahoo ID area, and a list of all the previously typed in IDs I ever used shows up. I like this feature, but I want to delete some of the IDs that firefox is remembering. I've tried Tools>Options>Advanced>OfflineStorage>ClearNow and restarted firefox but that doesn't seem to work, my IDs are still showing up on Yahoo...