Hi, I have been using yahoo mail for 1x to 2x years and yahoo mail was working fine from internet explorer to firefox over 2x years 14Nov2017 but after this date I could not login yahoo mail which was already login and stayed login before 14Nov2017 in Firefox 27.0.1 Then I tried Internet Explorer 11 which has never login yahoo mail before and it worked Both Firefox 27.0.1 and Internet Explorer 11 running on the same OS Windows 8 in a notebook I have tried to delete cookies and cache; set home page to hk.yahoo.com and then close firefox delete following files which will be re-created when invoking firefox content-prefs.sqlite cookies.sqlite cookies.sqlite-shm cookies.sqlite-wal permissions.sqlite at C:\Users\Username\AppData\Roaming\Mozilla\Firefox\Profiles\yyzlecc7.default Cache OfflineCache startupCache at C:\Users\Username\AppData\Local\Mozilla\Firefox\Profiles\yyzlecc7.default open firefox hk.yahoo.com pop-up; click sign-in; enter username (without @yahoo.com.hk) password; login failed Invalid passwor please try again open Internet Explorer 11; hk.yahoo.com; click sign-in; enter username (without @yahoo.com.hk) password; login successful and can see mails; send and receive mails I am 100% sure I enter username password correctly at both Firefox and Internet Explorer my email is username@yahoo.com.hk I would rather the login failed message were firefox 27.0.1 not supported at hk.yahoo.com after 14Nov2017; if invalid paasword, why could I immediately login hk.yahoo.com with the same username password using Internet Explorer 11? I have read many cor-el replies and found very helpful Looking forward to reply and thanks jac-k