About a week a go, I started getting a "error 404, not found" error when I tried to log into Yahoo mail on one account and a few days later, it started happening to my other Yahoo e-mail account. I upgraded to 4.0 and no change. This problem seems to be isolated to my home PC which is running XP. I have had no problems logging into my Yahoo e-mail account using Firefox from other computers and all other browswers ( Windows 8, Safari and Chrome )work on the same computer which is giving me trouble from Firefox.